Two times a number is divided by 3 more than the number. If the result is 7, then what was the original number?

[2x] / [ x + 3]  = 7     multiply both sides by x + 3

2x =  7 [x + 3]     simplify

2x = 7x + 21        subtract 7x from both sides

-5x  = 21       divide both sides by  -5

x = -21/5