 In this video, practice problem two, we're asked to find X given the information that the circle and segments are tangent. We have a theorem that says if two segments from the same exterior point are tangent to a circle, then they are congruent. That means from this point, this segment and this segment are each tangent to the circle at different places, and that makes them congruent to each other. And at the same time, these two pieces would be congruent to each other as well. So this is a fairly simple problem of setting pieces equal to each other, but it's important to realize where to start. If we were to start by setting up the equation that y minus five equals x plus four, that's not going to work for us because we have two variables and they're in x and a y, and we won't be able to solve for that. So we need to know in these problems to start with an equation where we only have one variable. And in this case, setting up the equation y equals ten, we don't have to do anything further to solve for y, we're already there. But remember we're asked to find x in the problem, so we need to use that information once we solve for x and plug it in over here. If we know that this segment is y minus five, we're going to plug in the fact that y equals ten and now this piece becomes a value of five. This segment right here equals five, so now we can set that equal to x plus four. We no longer have x and y in the equation. We only have x and now we can simply solve for x and we get x equals one and we're done.