
Step-by-step explanation
the perimeter of a triangle is the sum of the 3 lengths, so

then,
Step 1
definde the perimeter of triangel SQT

Step 2
definde the perimeter of triangle PQR

Step 3
as the triangles are congruent, the ratio of 2 perimeters must be the same, so

Step 4
finally, replace x in PQ to find the measure

I hope this helps you