Let's rename angle BAC to w. Now, we have four angles: w, x, y, and z. We know that w + y + z has to equal 180 degrees, because a triangle's three angels always adds up to 180 degrees. We also know that w + x equals 180 degrees, because they are on the same line. These two phrases are equal:
This is Pythagorean's Theorem, with one leg being 10 and the hypotenuse being 16. Using those values in the theorem looks like this: and and so Take the square root of both sides to find that b = 12.5
