 In order to find the area of this triangle, we're still going to use the area formula one-half base times height. However, we have a problem. If we use AC as the base, then the height is 12. However, we don't know how long that base is. We know the height, but we don't know the base. And so in order to figure out that base, we're going to have to use the Pythagorean theorem a little bit. So if we consider the entire triangle ABD, then in that triangle, we know let's call this a leg. Here's another leg, and we want to find the hypotenuse. So we could say 12 squared plus leg squared is equal to 20 squared. 12 squared, of course, is 144. That was supposed to be squared. 20 squared is 400. And if you subtract 144 from 400, you get that leg squared is equal to 256. And the square root of 256 is 16. So that leg is 16 units long. In other words, this entire length here is 16. And if a little piece of it was 5, then what's left over is that this base length must be 11. Because 16 minus 5, of course, is 11. So that was 16 units long. All right, now we have enough information to find the area of the triangle. Area is 1 half times base, which we established was 11 times the height, which is 12. And so our area, if you plug that into your calculator, you get that the area is 66 square units.