PR = PQ + QR [P-Q-R]
∴ PR = 6 + 10 = 16 units
Chords TS and RQ intersect externally at point P.
PQ × PR = PS × PT [Theorem of external division of chords]
∴ 6 × 16 = 8 × PT
∴ PT = (6 x 16)/8 = 12 units But,
PT = PS + TS [P – S – T]
∴ 12 = 8 + TS
∴ TS = 12 – 8
∴ TS = 4 units