3. Two angles and included side (ASA congruence theorem).
Reason: This is because, it is given that angle Q is congruent to angle T and line QR is congruent to line TR. Also, we proved in step 2 that [tex]\angle PRQ\cong\angle SRT[/tex]. Thus, we have two angles and the side included as congruent and thus, the two triangles are congruent.
4. CSCT (Corresponding Sides of a Congruent Triangle)
Reason: PR and SR are the corresponding sides of the congruent triangles [tex]\Delta PRQ[/tex] and [tex]\Delta SRT[/tex], therefore, by the CSCT these corresponding sides have to be congruent.
