Draw a line AB parallel to PQ, so AB∥PQ and PQ∥RS, so AB∥RS.
It is known that the sum of two interior angles on the same side is 180∘, therefore,
∠QXM+∠XMB=180∘
∠XMB=180∘−135∘
∠XMB=45∘
It is also known that the alternate interior angles are equal, so,
∠BMY=∠MYR
∠BMY=40∘
Now, ∠XMY=∠XMB+∠BMY
=45∘+40∘
=85∘