If you don’t know what a number is, you should substitute it for x and make an equation with the information you have been given. This gives:
(x + 8) x 2 = x - 11
Then, solve:
2x + 16 = x - 11
2x = x -27
x = -27
This can then be checked by using the number in the original text.
-27 + 8 = -19
-19 x 2 = -38
-38 is 11 less than -27.
Hope this helps :)
