Hope these are in fact what you mean with your questions. Just had me confused as they're in the calculus section. I think it should be in the trigonometry section.
Ignore this if it's totally not what you're getting at.
There are various ways of solving each of these questions. Below are just the methods I prefer to use. Using different trig ratios and angles should give the same answer.
To make solving these kinds of questions easier in future, try to become VERY familiar with Pythagoras' Theorem and SOH-CAH-TOA.
Alternatively, the angle of depression from the balloon is the same as the angle of elevation from the Rangers HQ (alternate angles), so you could also use the tan ratio in conjunction to this angle. Each will give the same answer.