An isosceles triangle has two sides equal and two angles equal. It is given in the problem that ∠Y is equal to a². We can solve for the remaining angles and the solution is shown below:
180°=∠X+∠Y+∠Z
180°=∠X+a° +∠Z
180°-a°-∠Z=∠X
If ∠Z is the same with ∠Y, then ∠X is equal to 180°-2a°.