Since the angle between two tangents drawn from an external point to a circle is supplementary to the angle subtended by the line segment joining the point of contact at the centre,
i.e., ∠POQ + ∠PTQ=180°
But ∠PTQ = 70° (given)
∴ ∠POQ = 108° – ∠PTQ
= 180° – 70° = 110°