Answer:
63.16 in approx.
Explanation:
Let the shorter leg be S. Then the longer leg is L = 3S + 3.
The formula for the area of a triangle is A = (1/2)(base)(height). Here, that works out to A = 84 in^2 = (1/2)(S)(3S + 3).
Simplifying, we get 168 in^2 = S(3S + 3), or
3S^2 + 3S - 168 = 0, or
S^2 + S - 56 = 0. This factors as follows: (S - 8)(S + 7) = 0, so the positive root is S = 8. We discard the negative root.
Thus, the shorter leg length is 8 and the longer leg length is 3(8) + 3, or 27.
According to the Pythagorean Theorem, the hypotenuse length is given by
L^2 = 8^2 + 27^2, or
L^2 = 64 + 729 = 793.
L = hypotenuse length = √793, or approx. 28.2 in.
Then the perimeter of the triangle is 8 + 27 + 28.2 in, or approx. 63.16 in