Question 619550
Let {{{ n }}} = the number of city miles driven
{{{ 4n }}} = the number of highway miles driven
{{{ n + 4n = 300 }}}
{{{ 5n = 300 }}}
{{{ n = 60 }}}
{{{ 4n = 240 }}}
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In the city:
{{{ 60 / 20 = 3 }}} gallons
On the highway:
{{{ 240 / 30 = 8 }}} gallons
He used {{{ 3 + 8 = 11 }}} gallons