Math
posted by John .
Please help I have no Idea what to do here.
A box with an open top is to be constructed by cutting ainch squares from the corners of a rectangular sheet of tin whose length is twice its width. What size sheet will produce a box having a volume of 420 in^3 when a = 3?

You are cutting out 3inch squares at the four corners.
Make a diagram.
width of base  x inches
length of base  2x inches, (you said so)
height of box  3 inches
(x6)(2x6)(3) = 420
(x6)(2x6) = 140
x^2  18x + 36 = 140
2x^2  18x  104 = 0
x = (18 ± √1156)/4
= (18 ± 34)/4
= 13 inches or a negative
so the sheet must have been 13 inches by 26 inches