Question 407640
if W = Width of the prism, L = Length of the prism and
H = Height of the prism, the surface area A of a rectangular prism is given by
A = 2WL + 2LH + 2HW
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So as A = 166, H = 4 and W = 5 
166 = 2*5*L + 2*4*L + 2*5*4
166 = 10*L + 8*L + 40
-18*L = -166 + 40
-18*L = -126
    L = 7
So Length of the prism is 7 millimeters