Question

Solve by setting up the proper equation to describe the facts given and then carrying out the mathematical calculations to solve for the unknown variable(s).
The difference between two numbers is 3, and the sum of those two numbers is 21. What are the two numbers?

Answer 1

x - y = 3

x + y = 21

x = 3 + y

3 + y + y = 21

2y = 18

y = 9

x - 9 = 3

x = 12

Answer 2

x-y=3