Raymond B. answered 06/19/21
L=7+2S
H=8+S
H^2 = L^2 + S^2
(8+S)^2 = (7+2S)^2 + S^2
64 + 16S + S^2 = 49 +28S + 4S^2 + S^2
4S^2 +12S -15 = 0
S^2 + 3S = 15/4 complete the square, take half of 3 and square it, (3/2)^2 = 9/4, add to both sides
S^2 + 3S + 9/4 = 15/4 + 9/4
(S +3/2)^2 = 24/4 = 6
S +3/2 = + or -sqr6
S = -3/2 + sqr6 = about 2.45- 1.5 = 0.95 inches
L = 7+2(.95) = 8.9 inches
H = 8+.95 = 8.95 inches
8.95^2 = about 8.9^2 + 0.95^2
80.1 = about 79.21 + .90= 80.1