A. To find the altitude of the top of the hill, we need to add 387 and -171.
387 + (-171) = 216
Therefore, the altitude of the top of the hill is 216 feet.
B. To find how much higher checkpoint 2 is than checkpoint 1, we must subtract the two values:
2,063 - (-43) = 2,106
Hence, checkpoint 2 is 2,106 feet higher than checkpoint 1.