The length of TS is 12.
Since TU is parallel to QR, we can form a pair of similar triangles:
TSU ~ QSR
From this similarity, we can set up a proportion to find the length of TS:
TS/SU = QS/QR
We know that QS = 30, SU = QR - TU = 35 - 21 = 14, and QR = 35. Plugging these values into the proportion, we get:
TS/14 = 30/35
Solving for TS, we get:
TS = (14 * 30) / 35
TS = 12
Therefore, the length of TS is 12.