Math Game Basic Functions

import time, random, sys
from tkinter import *
from threading import Timer

#Global variables to be set

global endGame
global gameTime
endGame = False
gameTime = 20
#functions required throughout the game
def runTimer(x):
    t = Timer(x,time_up) # x is amount of time in seconds
    t.start()
    mathFunction()
def time_up():
    print('your time is up!')
    global endGame
    endGame == True
    print (endGame)
    print('your time is up!')

def mathFunction():
    global endGame
    while endGame == False:
        Int1 = random.randint(0,20)
        Int2 = random.randint(0,20)
        Int3 = random.randint(0,20)

        if Int1 > Int2:
            answer = (Int1 - Int2) * Int3
            print ('(',Int1,'-',Int2,') x ',Int3)

        elif Int2 > Int1:
            answer = (Int2 - Int1) * Int3
            print ('(',Int2,'-',Int1,') x ',Int3)

        userInput = 0

        while True:

          try:
             userInput = int(input("Enter your answer: "))
          except ValueError:
             print("Not an integer!")
             continue
          else:

              if userInput == answer:
                  print('Correct')
                  break
              else:
                  print('Wrong')
                  break





#Display the first input as to whether the player would like to play

choice = ""

while choice != "n":

    choice = str(input('Would you like to play?(y/n)'))

    if choice == 'y':
        runTimer(20)
        while endGame == False:
            mathFunction()
    elif choice == 'n':
        break