 In these examples, we're going to use what we just learned about the properties of a square r. So in this problem, we are told that su is equal to 2x minus 8 and qA is equal to 3x minus 25. The first thing that we want to do is solve for x. Well, so if we look at this picture, su is a diagonal and qA is a diagonal. And because we just learned that squares share the properties of rhombite and rectangles, and because we know a property of a rectangle is that the diagonals are congruent, we can set up 2x minus 8 has to be equal to 3x minus 25. Solve this for x, so I'm going to subtract the 2x. It gives me negative 8x equals x minus 25, and then add 25 to both sides so we get x equals 17. Then it asks us to find su, and so that just means we are going to plug 17 back in for x. So 2 times 17 minus 8, and 2 times 17 is 34. 34 minus 8, we get 26. In order to do this problem, we can see that we are working with the measure of angle 3. And because we know that this is a square, the first thing that we know is that this is a 90-degree angle, angle u is a 90-degree angle, and then we also know that the diagonals bisect the opposite angles, which means angle 3 has been bisected. So if I take 90 and divide by 2, I know that angle 3 has to equal 45 degrees. And if I know that angle 3 has to equal 45 degrees, then I can set 2x minus 13 equal to 45, and then go ahead and solve for x. So if I add 13 to both sides, I get 2x equals 58, and divide both sides by 2, we get x equals 26. So again, because we know that angle u is a right angle, and because we know the diagonal has bisected it, that's why angle 3 is equal to 45 degrees, 90 divided by 2.