The fraction for mashed banana is 7/8.
The fraction of cup for mashed strawberries is 5/6.
Multiply the fraction 7/8 by 3/3 to obtain the same deniminator.
Multiply the fraction 5/6 by 4/4 to obtain the same denominator as fraction 21/24.
So Sam can write 7/8 as 21/24 and 5/6 as 20/24.