Midpoint/Segment Addition Postulate

Using the diagram, answer the question below.

Matt and Britney are on their way to Ann Arbor to see a University of Michigan football game. According to their GPS, the distance from Grand Rapids to Ann Arbor is 132 miles. They planned to stop for breakfast in Lansing, which is the midpoint of the trip, but they had to stop for gas. If Lansing is still 19 miles away from the gas station, how many miles have they traveled so far?

What theorems did you use to solve this problem?