Triangle abc is similar to triangle lmn by the similarity postulate

Same as Angle B. 90 degrees.

Step-by-step explanation:

If triangles are similar then they have the exact same angle measures. Angle m will have the same value as angle B. If angle B's measure is not found, then find it by adding angle A and angle C together and subtract from 180.

The picture is cut off but if A =60 and C=30 then 60+30=90 and 180-90=90. Angle B and M are both 90 degrees.