Question 832818
x for height
y for width
z for length


x=4y, and z=5+y, then volume formula for your box is {{{xyz=(4y)*y*(y+5)=4y^3+20y^2}}}.


You are given the volume:
{{{4y^3+20y^2=125}}}
{{{highlight(4y^3+20y^2-125=0)}}}
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Try Rational Roots Theorem with synthetic division to test for roots.
Maybe try a graphing calculator to make this easier.

Not quite to the accuracy you want, but y=2.1 approximately.