Step-by-step explanation:
Let x equal the width of the box and x + 15 equal the length of the box. Subtract 6 (the amount cut out) from both of the these to get the following terms: (x+9) and (x-6). These are the length and width of the box respectively. We also know that the height of the box is 3. Plugging these into the formula for the volume of a box gives you:
3(x+9)(x-6)=1092
Expanding this out gives:
3x^2+9x-162=1092
Subtract 1092 from both sides to make the quadratic equation equal zero. Plug the a, b and c coefficients into the quadratic formula (or factor) to find x.
3x^2 +9x-1254 = 0
a = 3 b = 9 c = -1254
I hope this helps :)