C++ Random number generator, isnt random but always returns the same number

Hi im looking for RandNum to generate a number between 2-10, and then that number being taken away from 15.

Right now, every time the program is executed, the number taken away from 15, (PerseusHealth) is 7. How do i fix this, and make it random?

void desertpath()
{
int scorpianchoice; //the option the player chooses.
int Maxhit = 10; //Max hit the scorpian can do
int Minhit = 2; //Min hit the scorpian can do

int randNum = rand()%(Maxhit + Minhit) + Minhit; 
int healthremaining = PerseusHealth - randNum; //health left in option1.


if(scorpianchoice == 1)
{
    cout << "You run under the Scorpians Legs in hopes to escape " << endl;
    cout << "You are hit by the scorpians Sting for " << randNum << " hp!";
    cout << "You have " << healthremaining << "/15 HP Left!" << endl;
    cout << "You escape the Scorpian but not without taking some damage" << endl;
}