Question

A number if that number and the number b sum to 40.

Answer 1

`\huge \boxed{40-b}`

Explanation:

`\sf Let \ x \ be \ that \ number.`

`x+b=40`

`\sf Solve \ for \ x.`

`\sf Subtract \ b \ from \ both \ sides.`

`x+b-b=40-b`

`\sf Simplify \ the \ equation.`

`x=40-b`

Answer 2

40-b

Explanation:

x is the unknown number

x+b = 40

We want to find x

Subtract b from each side

x+b-b = 40 -b

x = 40-b

The unknown number is 40-b