 Here's an example from section 3-2. We need to solve for x and we need to solve for y. Now in three of those angles, two of them have an x and only one has a y. And so it'll be easiest if we solve for x first. This angle and that angle are somehow related. Now they don't have a good proper name like alternate interior angles and they're not corresponding angles, they're not consecutive interior angles. So we're going to have to do a little bit of reasoning first. I know that the blue angle and the green angle, if I move this green angle up to its corresponding place, would make a linear pair. So that means that these two angles, the blue and the green, are supplementary. If they're supplementary, that means I can add them together to make 180 degrees. So the blue angle plus the green angle, 3x, I know together those two angles add up to 180 degrees. So solve for x. First we'll go through and collect like terms. I got a 9x and 3x together makes 12x plus 12 is equal to 180. Subtract 12 from both sides gives us 12x is equal to 168. And then divide both sides by 12, that leaves you with x is equal to 14. So I've solved for x, now it's my job to solve for y. So the angle that includes y is this angle down here, this red angle. And I know that that angle along with the blue angle are alternate exterior angles. And alternate exterior angles must be congruent. So the blue angle must be equal to the red angle, 4y minus 10. But we know that x is actually equal to 12. And so we can rewrite this side equation as 9 times 12 plus 12 is equal to 4y minus 10. And then we have to solve for y. No wait, x is not 12, x is 14. Oops, mistake. All right, so 9 times 14 plus 12 is equal to 138. And that equals 4y minus 10. Add 10 to both sides, that gives us 148 equals 4y. And then divide to both sides by 4, it gives us that y is equal to 37. So that's one of our answers. And then previously we had that x was 14.