Answer:
Δ MNO ≅ Δ RST
Explanation:
In naming the congruent triangles follow the same order, that is
M is the vertex with 79° and R is the vertex with 79°
MN = 21 and RS = 21
These are the first 2 letter names of the triangles, that is MN and RS
O and T are the third, thus
Δ MNO ≅ Δ RST