Since we know that the angles of a triangle add together to 180° and that the right angle is 90°, we know that 25° + 90° + y = 180°.

This is the same as saying that 115° plus the value of y adds up to 180°. What must be the measure of angle y?

180° − 115° = 65°

65°

Follow the same steps as in part (a). Remember that the sum of the angles of a triangle is 180°.