Question 789282
Let {{{ x }}} = gallons of 12% solution needed
{{{ .12x }}} = gallons of salt in 12% solution
{{{ .18*10 = 1.8 }}} gallons of salt in 18% solution
--------------------
First find for 14%
{{{ ( .12x + 1.8 ) / ( x + 10 ) = .14 }}}
{{{ .12x + 1.8 = .14*( x + 10 ) }}}
{{{ .12x + 1.8 = .14x + 1.4 }}}
{{{ .02x = .4 }}}
{{{ x = 20 }}}
----------
And find for 16%
{{{ ( .12x + 1.8 ) / ( x + 10 ) = .16 }}}
{{{ .12x + 1.8 = .16*( x + 10 ) }}}
{{{ .12x + 1.8 = .16x + 1.6 }}}
{{{ .04x = .2 }}}
{{{ x = 5 }}}
----------
between 5 gallons and 20 gallons of 12% salt
solution should be added