Question 408285
(final ounces of salt)/(final ounces of solution) = 7%
salt in 5% solution= {{{.05*28 = 1.4}}} ounces
Let {{{x}}} = ounces of water evaporated from solution
{{{1.4/(28 - x) = .07}}}
{{{1.4 = .07*(28 - x)}}}
{{{1.4 = 1.96 - .07x}}}
{{{.07x = .56}}}
{{{x = 8}}}
8 ounces of water must be evaporated
check:
{{{1.4/(28 - 8) = .07}}}
{{{1.4/20 = .07}}}
{{{1.4 = 1.4}}}
OK