How do I know that? Well, they both have a right angle right over here. They both share this angle. So if they have two angles in common, then all three angles must be in common. So they are similar triangles, which means the ratio between corresponding sides must be the same. So we know that the ratio of x to y must be the ratio of this entire base, which is x plus 10, to the height of the larger triangle, 220. And right there, we have a relationship between x and y.