Answer:
$0.45
Explanation:
The current price of a gallon of gasoline = $3.15.
The price when Ryan's mother started driving = 1/7 of the current price.
[tex]\begin{gathered} \frac{1}{7}\text{ of \$3.15} \\ =\frac{1}{7}\times3.15 \\ =\$0.45 \end{gathered}[/tex]The price of gasoline per gallon when Ryan's mother started driving was $0.45.
