I need to show all work. :/
In every case, the two different x expressions are equal. Set them equal then solve the equation for x. For example, in #7, 7x+ 3= 10x- 9. Subtract 7x from both sides, 3= 3x- 9, then add 9 to both sides, 12= 3x, and finally divide both sides by 3 to get 4= x.