A certain kind of fuel is 1515high octane and 4545regular octane. If high octane costs three times as much as regular octane, what fraction of the cost of the fuel is due to the high octane?
Choose the correct choice from the following choices
A) 1/5 B) 2/3 C) 3/7 D) 3/5 E) 4/5
let x be the amount of fuel   high octane = x/5   regular = 4x/5   price of regular = y   price of high octante = 3y   cost of high octane in the fuel = 3y * x/5   total cost = 3y * x/5 + 4x/5 * y   % = cost of high octante / total cost   = 3/7   Answer is 3/7
<result>C</result>
A certain kind of fuel is 1515high octane and 4545regular octane. If high octane costs three times as much as regular octane, what fraction of the cost of the fuel is due to the high octane?