angle sum theory find Y

25
The angle sum theory says that the sum of all the interior angles in a triangle is 180 degrees.
Finding X
To solve for y, we must first find x. This way we know 2 of the interior angles. Luckily, angle x is a part of a linear pair.
Angle x and the angle with a measurement of 115 form a linear pair. Thus, we can create an equation to find x.
By subtracting 115 from both sides we know that x = 65.
Solving for Y
Now that we know x, we can find y. We know that one of the interior angles is 65 and that the other is 90 degrees. The square marking the bottom angles in the middle show that they are right angles.
Lastly, we can create a formula to find y with the angle sum theory.
Combine like terms
Subtract 155 from both sides
This means that the angle y is 25 degrees.