Im not sure how to answer this please help

Question

An automobile engine can run on a mixture of gasoline and a substitute fuel. If gas costs $3.60 per gallon and the substitute fuel costs $2 per gallon, what percent of a mixture must be substitute fuel to bring the cost down to $2.16 per gallon?

Answer 1

3.6-2.16= 1.44

2.16-2 =0.16

1.44/.16=

9

9 times as much $2 as $3.60

to get a mixture of $2.16