To find the arc measure of MN in the given triangle LMN, where angle L measures 37°, we can use the property of inscribed angles. An inscribed angle is half of the measure of the arc that subtends it.
In this case, since angle L is inscribed and subtends the arc MN, we can express the relationship as follows:
\[ \text{Measure of arc MN} = 2 \times \text{measure of angle L} \]
Given that the measure of angle L is 37°:
\[ \text{Measure of arc MN} = 2 \times 37° = 74° \]
Thus, the arc measure of MN is 74°.