Question

how many 5/8 are in 21 7/8

Answer 1

21 7/8 divided by 5/8 is 35

Answer 2

start with something simple:
how many 1/4 are in one =4
how many 1/3 are in one=3
how did you get that?

1 divided by 1/4 = 1 x 4/1 = 4
similarly
1 divided by 1/3 = 1 x 3/1 = 3

so,
21 and 7/8 = (21x8) + (7/8) = (168/8) +(7/8)
=175/8
so, 175/8 divided by 5/8 = 175/8 x (8/5)
you will notice the 8's cancel an you are left ith 175/5
=35