Question 415858
I assume he doesn't have to use all of the 15% solution.
Let {{{a}}} = gallons of 15% solution needed
Let {{{b}}} = gallons of water needed
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Salt in 15% solution = {{{.15*a }}}
(1) {{{ .15a / 10 = .1}}}
(2) {{{a + b = 10}}}
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(1) {{{.15a =1}}}
(1) {{{a = 6.67}}} gallons
and
(2) {{{6.67 + b = 10}}}
(2) {{{b = 3.33}}}
Yes, he only needs 6.67 gallons of 15% solution