Because 120° and (2x-10) are on opposite sides, they are equal. You can set 120 equal to 2x-10 (120=2x-10). Then cancel out 10 on each side by adding 10 (130=2x). After that, you want to take the 2 and divide 130 by it to give you 65. (65=x)
The answer to find X is 65