the calculator won't work so if this makes it to the internet is: 7x-4=3x+8

 7x - 4 = 3x + 8

Add 4 to both sides.

7x = 3x + 12

Subtract 3x from both sides.

7x - 3x = 12

4x = 12

Divide both sides by 4.

x = 12/4

x = 3

Check: 7(3) - 4 = 3(3) + 8

            21 - 4 = 9 + 8

            17 = 17   true

thanks