Question

The difference of two numbers is 3 the sum is 13 find the numbers

Answer 1

X-y=3
x+y=13

Add the two equations to get the following in order to solve for x:
2x=16
x=8

Next you substitute into x+y=13 to solve for y

8+y=13
y=5

Therefore, x=8 and y=5

Answer 2

X - y = 3
x + y = 13
Adding both equations
2x = 16
x = 8
y = 5