I suppose the triangular flag is measure within x-y plane, so the length = base and the width = height
Let x be the width
Then, we will know that the area of triangular flag is:
A = (1/2)(base)(height) = (1/2)(4x)(x) = 72
x2 = 36
x = 6 (Thus, height = 6 feet, base = 4(6) = 24 feet)
Then, for rectangular mat, we will have A = (14 + x)(x) = 72
x2 + 14x - 72 = 0
(x + 18)(x - 4) = 0
x = 4 (Thus, width = 4 feet, length = 14 + 4 = 18 feet)