Respuesta :

The total measure of all the angles in a triangle is 180°.

Since there is already a 90° angle, the other 2 angles must also add up to 90°.

The only answer that fits is x = 9.

Check:

9x7 = 63°

3x9 = 27°

Add up = 90°

:)

C (x=18)

is your answer