Answer:
TS = 11.
Step-by-step explanation:
Consider triangles UTO and UCS.
m < C = m < UTO (Given)
< U is common to both triangles.
Therefore triangles UTO and OCS are similar.
So corresponding sides are in the same ratio and:
5 / (TS + 4) = 4/ (7+5)
5 * (7 + 5) = 4(TS + 4)
TS + 4 = 5*12 / 4
TS + 4 = 15
TS = 11.
