Question

How is the answer 143?

Answer 1

Here's the problem as a drawing, so we can work with it easier.


Would it help if I told you <GHK was a right angle?

Answer 2

one approach
tan(gkh) = 4/12 = 1/3
inverse tan = 18.4
RH = RK so sum of RHK and RKH = 2*18.4 = 36.8
angles in a triangle add up to 180
180 - 36.8 = 143.2 to the nearest degree = 143

Answer 3

@DDCamp yes, it subtends a semicircle so it is a right angle.