PLz answer for this question . I had asked this question previously also . I could not find the same question asked by any other student . SO plz answer this .

We know that the angle subtended by an arc at the centre is double the angle subtended by it at any point on the remaining part of the circle.

 

Therefore,

angle y = 2* angle z

angle x = 2* angle t

 

Adding, we get,

angle x + angle y = 2(angle t + angle z)