step 1
Find the unit rate
divide the total miles by the total gallons of gas
so
476/14=34 miles/gal
Let
y ------> the distance in miles
x -----> the number of gal
we have that
the linear equation is equal to
y=34x
part 2
If y=578 miles
Find the value of x
substitute in the equation
578=34x
solve for x
x=578/34
x=17 gallons