Question 1058745
Let {{{ x }}} = pounds of original solution
{{{ .1x }}} = pounds of salt in original solution
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The amount of salt in solution does not change
{{{ .1x / ( x - 40 ) = .15 }}}
{{{ .1x = .15*( x  - 40 ) }}}
{{{ .1x = .15x - 6 }}}
{{{ .05x = 6 }}}
{{{ x = 120 }}}
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The original solution was 120 pounds
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check:
{{{ .1*120 = 12 }}} pounds of salt
and
{{{ 12 / ( 120 - 40 ) = 12/80 }}}
{{{ 12/80 = .15 }}}
OK