Question 1054028
Let {{{ a }}} = ml of water needed
Let {{{ b }}} = ml of 25% alcohol solution needed
{{{ .05*75 = 3.75 }}} ml of alcohol in 
your final solution
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(1) {{{ .25b / ( a + b ) = .05 }}}
(2) {{{ .25b = 3.75 }}}
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(2) {{{ b = 3.75/.25 }}}
(2) {{{ b = 15 }}}
and
(1) {{{ .25b = .05*( a + b ) }}}
(1) {{{ .25*15 = .05*( a + 15 ) }}}
(1) {{{ 3.75 = .05a + .75 }}}
(1) {{{ .05a = 3 }}}
(1) {{{ a = 60 }}}
You need 15 ml of 25% solution 
and 60 ml of pure water
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check:
{{{ .25*15 / ( 15+ 60) = .05 }}}
{{{ 3.75/75 = .05 }}}
{{{ 3.75 = .05*75 }}}
{{{ 3.75 = 3.75 }}}
OK