Check the picture below.
we know that SR = RQ, we also know the angles at the point R are four right angles, triangles TRS and TRQ are sharing the same side of TR, that makes those two triangles congruent triangles by right-triangles LL theorem.
Likewise, triangles VRS and VRQ are sharing the side RV and thus those triangles are also congruent triangles by right-triangles LL theorem.
due to congruent triangles, then TQ = 3x+2 and 4x-1 = 15.
