We know that the angle of a straight line is 180°.
So we know that (5x-5) + (2x+10) = 180
We will then solve for x
5x - 5 + 2x + 10 = 180
7x + 5 = 180
7x = 175
x = 25 (just an explanation of how we get 25)
To get angle 1, we will then plug in x=25 into the first equation to get
5(25)-5 = 125-5 = 120°