-12 + 18. = 70

complete the square

Measure of ∠y is 90°

Step-by-step explanation:

We see that,

∠x and ∠y are vertical angles and ∠x, 40°, 50° are in a straight line.

Since, we know, Sum of angles in straight line is 180°.

Then, ∠x + 40° + 50° = 180°

i.e. ∠x = 180° - 90°

i.e. ∠x = 90°

Also, we know, 'Vertical angles have equal measures'.

So, ∠y = ∠x = 90°

Hence, measure of ∠y is 90°