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The capacity of the car’s tank was x gallons of gasoline. Before the trip, the tank was half full and therefore contained x/2 gallons of gasoline. During the trip, 30 percent of the gasoline in the tank was used, so the number of gallons lef was 70 percent of x/2, or \((\frac{7}{10})(\frac{x}{2})= \frac{7x}{20}\). After Diana added 8 gallons of gasoline to the tank, the total number of gallons in the tank was \(\frac{7x}{20} + 8\). Thus one correct choice is Choice B, \(\frac{7x}{20}+8.\) However, the question asks you to fnd all of the answer choices that represent the number of gallons of gasoline in the tank at the end of the trip. So you need to determine whether any of the other choices are equivalent to \(\frac{7x}{20} + 8\). Of the answer choices, only Choices A and C have the same constant term as Choice B: 8. So these are the only choices that need to be checked. Choice A, \(\frac{x}{2}-\frac{3x}{20}+ 8\), can be simplifed as follows.
\(\frac{x}{2}-\frac{3x}{20}+ 8 =\frac{10x}{20}-\frac{3x}{20}+ 8 =\frac{7x}{20}\)
So Choice A is equivalent to \(\frac{7x}{20}+ 8\). Choice C, \(\frac{3x}{20}+ 8\), is clearly not equivalent to \(\frac{7x}{20} + 8\). Thus the correct answer consists of Choices A and B.