. A gas station is charging $3 per gallon for gasoline. Let x represent the amount (in gallons) of gasoline purchased, and let f(x) represent the cost (in dollars) of x gallons of gasoline. A. Evaluate f(10) and f(15). B. When (i. E. For what value of x) is f(x) = 21?

(A) F(10) = 30, F(15) = 45

(B) x = 3

Step-by-step explanation:

According to the scenario, calculation of given data are as follows,

Charge for 1 gallon = $3

Amount of gasoline purchased = x

and x gallons cost = f(x)

So, cost for 1 gallon = f(x) ÷ x = 3

or f(x) = 3x

(A). So, for F(10)

Put value of F as 3, then

F(10) = 3 × 10 = 30

Similarly, for f(15) = 3 × 15 = 45

(B) f(x) = 21

we can put the value of f as 3, and then find the value of x,

3 (x) = 21

x = 21 ÷ 3

x = 7

quit

step-by-step explanation: