Ta gas station, 15 gallons of gas has a price of $17.55 and 18 gallons of gas has a price of $21.06. write a direct variation equation that relates the cost y of any number of gallons of gas x. how many gallons of gas can be purchased for $23.40?

A direct variation means, the value of the dependent variable,
varies based on the independent variable times some constant,
let us call it "k", so y=kx, whatever k is
so 


once you get what "k" is, plug it back in the original y=(k)x

then, how many gallons can be purchased with 23.40? namely
if y=23.40, what's "x"?   put the "k" value found and solve for "x"