Answer: 
Concept:
In a function f(x), it represents a function in terms of x or for x. Therefore, to find the values in the function, substitute values within the parenthesis to solve.
Solve:
<u>Given information</u>

<u>Need to find</u>

<u>Substitute (x + 4) to the position of x</u>

<u>Distributive property on the numerator</u>

<u>Combine like terms</u>


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Answer: I think the answer is B
Step-By-Step Explination:
First you find out what x is by doing 42 multiplying it by 0.1 witch equals 4.2 gallons per mile
Next you figure out what y is by doing 4.2y (witch is 4.2 times y)
Multiply everything by 2 then combine like terms