Answer:
1/4
Step-by-step explanation:
Total students = 80
Students taking both classes = 15
Students taking algebra class = 60
Students taking only algebra class = 60 - 15 = 45
Students taking only pre-calculus class = 80- (45+15) = 80 - 60 = 20
P( students taking pre-calculus but not algebra) = 20/80 = 1/4