PreCalc
posted by YKWCH .
A box is formed by cutting squares out of the corners of a flat piece of metal, and folding the sides up. What size cuts should I make to a 14in. by 20in. piece to get a volume of 270in cubed?

270 = x(142x)(202x)
4x^3  68x^2 + 280x  270 = 0
x = 1.4 or 4.2
not sure what tools you have to solve cubics. In this case a simple graphic method gives approximate results.
visit wolframalpha.com and type in
solve x(142x)(202x) = 270