Question

Find the missing numerator 7/8 = ?/32

Answer 1

These are equivalent.
7/8 is equivalent to 28/32

Why?
If you look at the denominators, 8 * 4  = 32
To get the numerator, you simply multiply 7 by 4 as well, which equals to 28.

Answer 2

To find a missing number in a fraction, set the problem up like $\frac{7}{8} = \frac{x}{32}$ .  Then, multiply the two opposite numbers: in this case, 7 and 32.  Then, divide by the remaining number (8) to get your answer. 

The answer is 28