Karen is thinking of two numbers. Their difference is 9 and their sum is 17. What are the numbers?

Answer 1

Let x be one number and y be the other number

x-y=9 their difference is 9

x+y=17 their sum is 17

In the first equation

x-y=9 add the y to both sides

x=y+9

Substitute that in the other equation

y+9+y=17

Combine like terms

2y+9=17

Subtract the 9 from both sides

2y=8

Divide both sides by 2

y=4

Plug that y value into either of th original equations to get x

x+4=17

X=13