We are trying to find the area of the final triangle. From the information given in the problem, we know the final triangle is 1/3 the size of the original. That means once we find the lengths of the sides of the new triangle, we just plug them into the area formula to find our answer.
12/3=4
18/3=6
A=1/2bh
A=1/2(4)(6)
A=1/2(24)
A=12 mm^2
