Answer:
The number of pages that Polina read was 90 and the number of pages that Marcus read was 18
Explanation:
Let
x -----> number of pages that Polina read
y ----> number of pages that Marcus read
we know that
x+y=108 ----> equation A
x=5y -----> equation B
substitute equation B in equation A and solve for y

Find the value of x

therefore
The number of pages that Polina read was 90 and the number of pages that Marcus read was 18