How to get previous Tkinter value to delete when user clicks a button and generate a new value?

from tkinter import *
import random as r
from collections import Counter

root = Tk()
root.title("Simple Mafs")
root.geometry("600x400")
root.resizable(False, False)


def open_gn():
    gn_wn = Tk()
    gn_wn.title("Simple Mafs - Generate a number")
    gn_wn.geometry("600x400")
    gn_wn.resizable(False, False)

    Label(gn_wn, text='                                                      ').grid(row=0, column=0)
    inst_gn = Label(gn_wn, text='Enter a minimum and maximum value(below 100)')
    inst_gn.config(font=("Yu Gothic UI", 12))
    inst_gn.grid(row=0, column=1)

    Label(gn_wn, text=" Enter a minimum value: ").place(x=295, y=100)
    entry_min = Entry(gn_wn)
    entry_min.insert(0, "0")
    entry_min.place(x=450, y=100)

    Label(gn_wn, text=" Enter a maximum value: ").place(x=295, y=200)
    entry_max = Entry(gn_wn)
    entry_max.insert(0, "99")
    entry_max.place(x=450, y=200)

    Label(gn_wn, text="Random value is: ").place(x=40, y=40)

    def generate_number():
        min_ = int(entry_min.get())
        max_ = int(entry_max.get())

        random_num = r.randint(min_, max_)
        d_rn = Label(gn_wn, text=random_num)
        d_rn.config(text=random_num, font=("Yu Gothic UI", 30))
        d_rn.place(x=40, y=100)

    Button(gn_wn, text="Generate", padx=220, pady=25, command=generate_number).place(x=25, y=280)

    gn_wn.mainloop()


def open_coin():
    c_wn = Tk()
    c_wn.title("Simple Mafs - Flip a Coin")
    c_wn.geometry("600x400")
    c_wn.resizable(False, False)

    Label(c_wn, text="                                                                                ").grid(row=0,
                                                                                                              column=0)
    Label(c_wn, text="Flip the coin below!", font=("Yu Gothic UI", 12)).grid(row=0, column=1)

    Label(c_wn, text='                    ').grid(row=1, column=1)

    coin_label = Label(c_wn, text="")
    coin_label.place(relx=0.5, rely=0.2, anchor='s')

    def flip():
        coin_values = ["Heads", "Tails"]
        coin_face = r.choice(coin_values)
        if coin_face == "Heads":
            coin_label.config(text="Coin: Heads")
        else:
            coin_label.config(text="Coin: Tails")

    coin = Button(c_wn, text='coin', padx=100, pady=90, command=flip)
    coin.place(relx=0.5, rely=0.5, anchor=CENTER)

    c_wn.mainloop()


def open_average():
    avg_wn = Tk()
    avg_wn.title("Simple Mafs - Averages")
    avg_wn.geometry("840x300")

    Label(avg_wn, text="              ").grid(row=0, column=0)
    avg_instruct = Label(avg_wn, text="Enter your values below to get the averages in mean, median, and mode(put a "
                                      "space between commas")
    avg_instruct.config(font=("Yu Gothic UI", 10))
    avg_instruct.grid(row=0, column=1)

    Label(avg_wn, text="                                     ").grid(row=1, column=0)
    entry = Entry(avg_wn)
    entry.grid(row=2, column=1)

    def calculate():
        list_data = entry.get().split(', ')
        list_data = [float(i) for i in list_data]
        mean = sum(list_data) / len(list_data)
        Label(avg_wn, text='Mean').grid(row=5, column=0)
        Label(avg_wn, text=str(mean)).grid(row=6, column=0)

        list_data_len = len(list_data)
        list_data.sort()

        if list_data_len % 2 == 0:
            median1 = list_data[list_data_len // 2]
            median2 = list_data[list_data_len // 2 - 1]
            median = (median1 + median2) / 2
        else:
            median = list_data[list_data_len // 2]
        Label(avg_wn, text='Median: ').grid(row=5, column=1)
        Label(avg_wn, text=median).grid(row=6, column=1)
        list_data_for_mode = Counter(list_data)
        get_mode = dict(list_data_for_mode)
        mode = [k for k, v in get_mode.items() if v == max(list(list_data_for_mode.values()))]

        if len(mode) == list_data_len:
            get_mode = ["No mode found"]
        else:
            get_mode = [str(i) for i in mode]

        Label(avg_wn, text="Mode: ").grid(row=5, column=2)
        Label(avg_wn, text=get_mode[0]).grid(row=6, column=2)

    Label(avg_wn, text="                                     ").grid(row=3, column=0)

    Button(avg_wn, text='Enter', command=calculate).grid(row=4, column=1)


def rand_stat():
    pass


Label(root, text="                                           ").grid(row=0, column=0)

title = Label(root, text="Welcome to Simple Mafs")
title.config(font=("Yu Gothic UI", 24))
title.grid(row=0, column=1)

button1 = Button(root, text="Generate a random number", padx=80, pady=25, command=open_gn)
button1.place(x=2.25, y=100)

button2 = Button(root, text="Calculate mean, mode, median, and range", padx=20, pady=25, command=open_average)
button2.place(x=325, y=100)

button3 = Button(root, text="Flip a Coin", padx=125, pady=25, command=open_coin)
button3.place(x=2.25, y=200)

button4 = Button(root, text="Calculator", padx=105, pady=25, command=rand_stat)
button4.place(x=325, y=200)

root.mainloop()

Skip to the open_gn() one because that's where the problem is. I want to make an app that can do statistics/random related stuff and in it, I want to create an app that can generate a random number. The app generates the number but the previous value stays and interferes with the current number being generated.