This is a trigonometry question, where a right angle triangle is created from the boat to the coast to the top of the light house.
x is the angle of elevation
Opposite is the height of the light house
Adjacent is the distance from coast
Tan(x) = opposite/adjacent
tan (59) = opposite/ 45
tan(59) x 45 = opposite
opposite = 74.893
The height of the light house (from sea level) is 75 foot.