Answer:
m < 1 = 72
Explanation:
Since we know that line l and line m are parallel and that p is one of their transversals, it sets up a situation where we can identify which angles are congruent (equal) to one another according to their positions.
In this case, we can see that < 3 and < 1 are in the same matching corners created by the transversal. When angles are in the same matching corners they are called corresponding angles - and according to the Corresponding Angles Postulate, corresponding angles are congruent.
Therefore, m < 3 = m < 1, and since it's given that m < 3 = 72, we know that m < 1 = 72 too.