The correct answer is 35.

Solution:
Consider the given equation.
+ 5 = 47 – 7

To determine the missing number, first, we need to find: 47 – 7.

Which gives:
47 - 7 = 40

Then,
+ 5 = 47 – 7

+ 5 = 40

Next, to find the missing number we find: 40 – 5.

Which gives:
40 – 5 = 35

So,
35 + 5 = 47 – 7

That is, number 35 makes the equation true.