A person takes a trip, driving with a constant speed of 90.5 km/h, except for a 28.0-min rest stop. The person's average speed is 73.2 km/h. (a) how much time is spent on the trip?
(b) how far does the person travel?

We have a segment AC and B is in the middle. So AB + BC = AC because the segment is in pieces. Because B is a midpoint, AB = BC. We now have

AB + BC = AC sum of a segment is sum of its pieces

AB + AB = AC B is the midpoint, so AB = BC

2x + 2x = 3x + 20 putting in for AB (twice!) and AC

4x = 3x + 20 collect like terms

x = 20 subtract 3x on both sides.

So x=20