Answer:
15 students (30% of the students in class) scores a 95 on a quiz.
Therefore the total number of students (100% of the students) in class is:
N = 15 x 100/30 = 50 (students)
(This calculation is inferred from a ratio that 15/N = 30/100).
Denote the number of students who scored a 95 on a quiz is a, the total number of students in class is b.
Then the equation that related a and b is:
b = (100/30) x a
Hope this helps!
:)