Determine the extent of South America from west to east along the equator.

First, we determine the extreme points of the continent along the equator, now only longitude is important.
In the west 81 °, in the east 33 °. We subtract the smaller one from the larger indicator (if the distance that needs to be determined would intersect 0 meredians, then the indicators would add up) and we get the length of the distance in degrees.
Further, we know that at the equator the length of 1 ° is 111 km.
We multiply 33 by 111 and we get 3663 km.