Answer: You need 3 gallons of gas
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Work Shown:
(1 gallon gas)/(4 oz of oil) = (x gallons of gas)/(12 oz of oil)
1/4 = x/12
1*12 = 4*x ...... cross multiply
12 = 4x
4x = 12
4x/4 = 12/4 ... divide both sides by 4
x = 3 gallons of gas is needed