Your answer to this question is definitely C!
Answer: h=10
Solving Steps:
45 = 1/2h x (4+5)
45 = 1/2h x 9
45 = 9/2h
10 = h
h = 10
That's an awfully broad question. Could you not be more specific?
A basic example: Suppose you are told that sin theta = 1/2. Solving this equation would require finding the measure of the angle theta. In this case the answer would be "30 degrees," or "pi/6 radians."