It costs $57.19 to fill up a 19 gallon gas tank and $54.18 to fill up an 18 gallon tank.

What is the constant of proportionality that relates the cost in dollars,
y, to the number of gallons of gas, x?

y=3.01x

Step-by-step explanation:

We can see that since 19 gallons cost $57.19 and 18 gallons cost $53.18, 1 gallon (19-18) must cost $3.01.

Therefore, y=3.01x

You can check this with algebra

5+2x=a

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