we know that
If two figures are congruent, then its corresponding sides and its corresponding angles are congruent
In this problem
we have that
MP=PL -----> is given
NP is a common side
is given
Triangle NML is an isosceles triangle
that means
NM=NL
therefore
the two triangles have two corresponding sides congruent and the angle between the two sides is congruent
so
the triangles are congruent by SAS
