Hey there!
This diagram shows two parallel lines (they will never intersect). This lines are crossed by another line called a transversal. This simple diagram can help us understand the nature of angles in our world.
The most important number to think about when it comes to this diagram is 180. A full circle is 360 degrees, and half of that is 180. Let's say that you are opening a shoe box. With the lid closed, there is no angle. If you open the lid straight up so that there is an L-shape, you have made a right angle, which is 90 degrees. If you open it so that it makes a line, you are now at 180 degrees. If you were to open the lid in a full circle, that would be 360 degrees, but the lid would probably break off!
We see that a straight line is a 180 degree angle. This means that 3y and the angle on the other side of the transversal right next to it (we'll call this angle A) should add up to equal 180 degrees. Angles that add up to equal 180 degrees are called supplementary angles. Looking again, we see that angle A and the 87 degree angle make up a straight line, so they are also supplementary. If 3y is supplementary with angle A and angle A is supplementary with 87, then 3y must be equal to 87. 3y and 87 are known as vertical angles because they are vertical of each other and meet at a point. Vertical angles are always congruent, so 3y is 87. We can just divide 87 by 3 to figure out what y is: 29.
There are also corresponding angles. These are angles that are the exact same but are in different places. For example, angle 87 is going to be the same thing as the supplementary angle to the bottom left of 3x because they are both to the left of the transversal and below the parallel line. Therefore, 3x is supplementary with 87. If you subtract 87 from 180, then you get 93. We divide by 3 to get x, giving us 31.
So, x=31 and y=29.
I hope that this helps! Have a wonderful day! :D
