Question 694274
Let h be the gallons used on highway. Let c be gallons used on city driving.
You are told
{{{h + c = 13}}} --> {{{c = 13 - h}}}
{{{34h + 26c = 414}}}
{{{34h + 26(13-h) = 414}}}
{{{34h + 338 - 26h = 414}}}
{{{8h = 76}}}
{{{h = 9.5}}}
{{{c = 13 - 9.5 = 3.5}}}
Use these values to calculate the miles driven for each type
{{{cityMiles = 26*c}}}
{{{HighwayMiles = 34*h}}}

you can do the rest