print("How many sides are in your regular polygon?")
x = int(input())
z = 360
from turtle import*
pencolor("red")
penup()
lt(90)
fd(260)
rt(90)
backward(10)
pendown()
y = 'z / x'
for a in range(round(int("x"))): #The number in the() is the number of sides in a regular polygon.
fd(50)
rt(y)#The number in () is 360/ the number of sides in a regluar ploygon.
round(int("x")) ？？ 这个不应该是 round(x) 就行么，或者直接不用round了，没必要啊，你前面这x已经是int了
还有那个变量y，直接写y = z / x 就行吧，不用引号、、如果要取整就 y = z//x
谢谢！