Question

The sum of two numbers is 39. Their difference is 15. What are the two numbers

Answer 1

Substitute x = 27 into:
x + y = 39
27 + y = 39
y = 39 - 27
y = 12                                                                                     
the answer is x=27 y=12

Answer 2

The answer is 7 and 22 because they are 15 part and add up to 29 and are 15 apart