a triangle's angles should all add up together to 180 degrees. Since a right angle is 90 degrees then you have your 60 degree angle that only leaves 30 degrees left.
A is right because it’s right triangle since it has a right angle. C is also right, x=30 because we have 60 degrees and 90 degrees. 60 plus 90 is 150 and a triangle is equal to 180 degrees 180-150 is 30
