We will have the following:
a) We have that in order to determine how much lower is checkpoint 1 than checkpoint 2, we find the difference between those values, that is:
[tex]x=-163-(-39)\Rightarrow x=-124[/tex]
So, checkpoint 1 is 124 ft lower than checkpoint 2.
b) To determine the altitude of the hill we will operate as follows:
[tex]a=-163+232\Rightarrow a=69[/tex]
So, the top of the hill is 69 ft above sea level.
