Alright. The way those 2 lines are intersecting tells me that 120 and the number opposite must be equal, therefore:
120 = (2x - 10)
so lets find x, in this case, it is simple arithmetic, we'll plug numbers:
60*2 = 120
120-10 = 110
Incorrect, however;
65 * 2 = 130
130 - 10 = 120
therefore,
120 = (2*65) - 10
120 = 120
x = 65