[tex]13 \dfrac{1}{2} \text { gallons} = 290 \dfrac{1}{4} \text { miles}[/tex]
Change to improper fractions
[tex]\dfrac{27}{2} \text { gallons} = \dfrac{1161}{4} \text { miles}[/tex]
Multiply by 4 on both sides
[tex]54 \text { gallons} = 1161 \text { miles}[/tex]
Divide by 54 on both sides
[tex]1 \text { gallons} = 43 \dfrac{1}{2} \text { miles}[/tex]