Distance, d, is directly proportional to the number of gallons of gas, g. Thus,
d α g
To turn alpha to equal sign, we insert a constant of proportionality, k.
d=kg
To find k, we use the given conditions.
476 = k (14)
k = 34
Therefore, the equation is,
d = 34g
and for travelling 578 miles,
578 = 34g
g = 17 gallons is needed.
