How to update a variable value everytime a tkinter button is pressed?

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Python

GUI

from tkinter import *

x = 0

def val_Changer(x):
global z
z = x + 1
print(z)
return z


def root():
root = Tk()

val_Updater = Button(root, text="Update Value (+1)", width=25, height=4, bg="Red", fg="White", command=lambda:val_Changer(x))
val_Updater.place(x=75, y=125)

root.title("Value Updater")
root.geometry("350x350")
root.resizable(False, False)
root.mainloop()

root()

Above if the code i've listed that isn't seeming to work. I'm trying to build a quiz where if the user clicks the right button than the variable will update +1. If the user manages to get the variable to 10 than he gets 10 percent. If i cant get this small peice of code working i can make my quiz. Please help a young programmer out because i've been trying for 2 weeks and im frustrated. I've tried the tkinter.IntVar() but i cant pass it as an argument into another function to calculate the score. P.S Im using windows 10 on python 3.4 w/ tkinter