Invalid Syntax Error - Average Calculator "IF" and "WHILE"

I have no idea what I'm doing wrong, but this is driving me up a wall. Why am I getting a Syntax error? I have to code an average calculator using a while statement, where "0" defines that the program needs to perform the calculation.

Here's the sample output my professor defined:

SAMPLE RUN

Enter test score 80

Enter test score 70

Enter test score 90

Enter test score 88

Enter test score 0

The average is 82.000%