Answer:
ST = 108km
Explanation:
In ΔPQR and ΔTSR,
∠PRQ = ∠TRS (vertically opposite)
∠PQR = ∠TSR (alternate interior)
∠QPR = ∠ STR (alternate interior)
Since all the angles are equal,
ΔPQR and ΔTSR are similar
Therefore, their corresponding sides have the same ratio

⇒ ST = 108km