Question

Twice bill's number added to 17 is 7. What is his number

Answer 1

Let b=bills number
2b+17=7
Subtract 17 from both sides
2b=-10
Divide both sides by 2
b=-5
Bill’s number is -5

I hope this helps )

Answer 2

-5.

-5 * 2 = -10
-10 + 17 = 7