Question

if -9 is added to a number and the sum is doubled, the result is 11 less than the number. Find the number

Answer 1

Suppose that x is the number we want :

- 9 added to it means :

`x + ( - 9) = x - 9`

And sum is doubled means :

`2 * (x - 9)`

The result is 11 less than the number which means :

`2 * (x - 9) = x - 11`

Now let's find the x ...

`2x - 18 = x - 11`

Add both sides 18

`2x - 18 + 18 = x - 11 + 18`

`2x = x + 7`

Subtract both sides x

`2x - x = x + 7 - x`

`2x - x = x - x + 7`

`x = 7`

Thus that number is 7

Answer 2

Answer: 7

let x be the number

2(-9 + x) = x - 11

-18 + 2x = x - 11

2x - x = -11 + 18

x = 7