Bill spent $147...$525-28%=$147
(0.33 m)·(0.19 m)·(0.20 m)·(3.28 ft/m)³ ≈ 0.4425 ft³
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Use the conversion factor in a way that cancels the units you don't want and leaves the units you do want.
18 is your final answer when been simplify
28 is the coefficient and the simplified expression is 28x + 35