Question 293907
Starting with the formula for the volume of a box:
{{{V = L*W*h}}} Substitute: V = 756, L = W+3, and h = 7.
{{{756 = (W+3)*W*7}}} Divide both sides by 7 and simplify..
{{{108 = W^2+3W}}} Rearrange into the standard form for a quadratic equation.
{{{W^2+3W-108}}} Solve by factoring.
{{{(W+12)(W-9) = 0}}} Apply the "zero product" rule.
{{{W+12 = 0}}} or {{{W-9 = 0}}} so...
{{{W = -12}}} or {{{W = 9}}} Discard the negative soltion as width cannot be negative,
{{{highlight(W = 9)}}}inches, and...
{{{L = W+3}}}
{{{highlight(L = 12)}}}inches.