Question 1154789
Let {{{ x }}} = ounces of 10% alcohol needed
-------------------------------
{{{ ( .1x + .15*18 ) / ( x + 18 ) = .11 }}}
{{{ .1x + 2.7 = .11*( x + 18 ) }}}
{{{ .1x + 2.7 = .11x + 1.98 }}}
{{{ .01x = 2.7 - 1.98 }}}
{{{ .01x = .72 }}}
{{{ x = 72 }}}
72 ounces of 10% alcohol are needed
-----------------------
check:
{{{ ( .1x + .15*18 ) / ( x + 18 ) = .11 }}}
{{{ ( .1*72 + .15*18 ) / ( x + 18 ) = .11 }}}
{{{ ( 7.2 + 2.7 ) / ( 72 + 18 ) = .11 }}}
{{{ 9.9 / 90 = .11 }}}
{{{ 1.1 / 10 = .11 }}}
{{{ 1.1  = 1.1 }}}
OK