How would I be able to add a score counter to a math quiz that includes functions? Any help is appreciated

Below I have created a Maths quiz in python. It consists of random equations to solve. The questions are generated using random numbers and functions that determine whether the question is add or subtract. I have completed the quiz, but I have tried adding a score counter so that if the user gets a question right, a point is added on. I am unsure how to do this, as I have tried implementing the score into the functions and it does not work. any help would be appreciated. Here is the code:

import random
#Asks for name
name = input("What's your name?")
#Stops user from entering invalid input when entering their class
classchoices = ["A","B","C"]
classname = input("What class are you in?")
while classname not in classchoices:
    classname = input("Not a valid class, try again:")

print(name, ",", classname)
print("Begin quiz!")

questions = 0
a = random.randint(1,12)
b = random.randint(1,12)


def add(a,b):
    addQ =  int(input(str(a) + "+" + str(b) + "="))
    result = int(int(a) + int(b))
    if addQ != result:
        print ("Incorrect! The answer is", result)

    else:
        print("Correct")





def multiply(a,b):
    score = 0
    multQ =  int(input(str(a) + "X" + str(b) + "="))
    results = int(int(a) * int(b))
    if multQ != results:
        print ("Incorrect! The answer is", results)

    else:
        print("Correct")



def subtract(a,b):
    subQ =  int(input(str(a) + "-" + str(b) + "="))
    resultss = int(int(a) - int(b))
    if subQ != resultss:
        print ("Incorrect! The answer is", resultss)
    else:
        print("Correct")

for questions in range(10):
    Qlist = [add, subtract, multiply]
    random.choice(Qlist)(random.randint(1,12), random.randint(1,12))
    questions += 1



if questions == 10:
    print ("End of quiz")