Explanation:
(j)
because of the angles of 2 intersecting lines are the same (just left- right mirrored) on both sides of an intersected line, we can say that the
inner angle STR = inner angle PTQ.
we know that
P = S = 90°
so, again, the always and forever rule : the sum of all angles in a triangle is 180°.
and therefore, since 2 pairs of angles are already equal between the triangles, we know the third pair of angles (Q and R) must be equal too.
so, we know all 3 pairs of angles are equal, and one pair of sides is equal (PQ and SR).
so, we can apply e.g.
ASA (angle- side - angle) as for P-PQ-Q to S-SR-R to prove that PQR is congruent with SRQ.