the car rental is 38.15 + 12 1/2 per mile or
[tex]\bf \textit{rental function R(x) then is }
\\\\
R(m)=38.15+12\frac{1}{2}m\implies R(m)=38.15+\cfrac{25}{2}m
\\\\
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\textit{she drove 380.5 miles}\implies m=380.5\\\\
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R(380.5)=38.15+\cfrac{25}{2}(380.5)\impliedby \textit{she owes that much}[/tex]
now, we're assuming she drove that in 1day, thus she's only getting charged 38.15, for 1 day :)