Twice the sum of a number and 7 is equal to three times the difference of the number and 8.

First, set up what you know. Twice the sum of a number and seven means: 2x+7. Three times the difference of the number and 8 is 3 (x-8).

Set both of them equal to each other and you'll get this:

2x+7 = 3 (x-8)

Afterwards just follow through with algebra.

2x+7 = 3x - 24

2x + 31 = 3x

31 = 3x - 2x

31 = x

Afterwards check your work to see if it is correct.

2 (31) + 7 = 3 (31 - 8)

62 + 7 = 3 (23)

69 = 69