First you have to find x angle because it will correspond with the DFE angle and then you can find the AFE angle.
To do this, you add angles BFC and CFD. BFC is 50° and CFD is 90° (because it is a right angle). 50+90=140°. Then to find x, you subtract 140° from 180°, which is 40°. So x=40°.
Then, since you know that x corresponds with angle DFE, you subtract 40°(x/DFE angle) from 180°(straight line) and you get 140°. So, ∠AFE=140°.
