p = d*1.04 + 18 (Based on the question. 4% Sales Tax +0.18 cents per gallon)
d = (p-0.18)/1.04
Answer is D
How is the bolded part even true? Doesn't the question really say: p/gallon = d*1.04 + 18/gallon
Thus, how can you "remove" the fractions p/gallon and 1/gallon from both sides without multiplying gallon with d*1.04? What am I missing?
Because I easily understand the question when it is done as you say, but logically I just cannot seem to understand WHY the fraction /gallon is not included in your equation.