Question 755847
Let {{{ w }}} = quarts of water to be added
{{{ .8*13 = 10.4 }}} = quarts of antifreeze in 80% solution
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{{{ 10.4 / ( w + 13 ) = .65 }}}
{{{ 10.4 = .65*( w + 13 ) }}}
{{{ 10.4 = .65w + 8.45 }}}
{{{ .65w = 1.95 }}}
{{{ w = 3 }}}
3 quarts of water need to be added
check:
{{{ 10.4 / ( w + 13 ) = .65 }}}
{{{ 10.4 / ( 3 + 13 ) = .65 }}}
{{{ 10.4 / 16 = .65 }}}
{{{ 10.4 = .65*16 }}}
{{{ 10.4 = 10.4 }}}
OK