First, you have to know the formula of finding the area of a triangle. That is bh1/2. You multiple the base and height together and multiply it by 1/2 or divide by 2. You put in the info they gave you in the formula, after that you get 105/8. That is obviously not one of the choices and it is an improper fraction. The way to make it into a whole fraction is to do 105 divided by 8. Then, you get 13, which is the second answer. Finally, the area of the triangle is 13 1/8 squared mm.