[SPIDER]

Suppose that:
H = tall of Head
B = tall of Body
T= tall of Tail

Given:
H = 6
T = 2H + 0.5B
B = H + T

After Calculation:
H = 6 in
B = 36 in
T = 30 in
Total = 6 + 36 + 30 = 72 in

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