The bottom triangle that has a 40° is an isosceles triangle, therefore the other angle at the bottom right is also 40°. This leaves the top angle to be 100°.
180=40+40+x
180=80+x
x=100
Now, to find ∠2, you can tell it is a supplementary angle. Therefore, the 2 angles add up to 180°
180-100=∠2
80°=∠2
The problem states that ∠2 is 9x-1. We know that ∠2 is 80°. We can solve for x.
