Here, AQST is a cyclic quadrilateral.
We know, in a cyclic quadrilateral, the sum of opposite angles are supplementary, i.e. 180o.
Here, ∠A=∠TAQ and ∠S=∠TSQ are opposite angles.
Then clearly, ∠A+∠S=180o
⟹ ∠TAQ+∠TSQ=180o.
That is the sum of ∠TAQ and ∠TSQ is 180o.