Question 1122001
Let {{{ x }}} = ml of solution B used
{{{ x - 300 }}} = ml of solution A used
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{{{ .19*( x - 300 ) = alcohol in solution A
{{{ .12x }}} = alcohol in solution B
{{{ 377 }}} = alcohol in solution A and B
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{{{ .12x + .19*( x - 300 ) = 377 }}}
{{{ .12x + .19x - 57 = 377 }}}
{{{ .31x = 434 }}}
{{{ x = 1400 }}}
And
{{{ x - 300 = 1400 - 300 }}}
{{{ x - 300 = 1100 }}}
She uses 1100 ml of solution A
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Check:
{{{ x + x - 300 = 1100 + 1400 }}}
{{{ 2x - 300 = 2500 }}}
{{{ 2x = 2800 }}}
{{{ x = 1400 }}}
OK