Question 1129217
Let {{{ a }}} = gallons of pure antifreeze drained from radiator
Let {{{ b }}} = total gallons of mixture removed from radiator
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(1) {{{ a = .45b }}}
(2) {{{ ( -a + b ) / 4 = .6 }}}
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(2) {{{ -a + b = 2.4 }}}
(2) {{{ -.45b + b = 2.4 }}}
(2) {{{ .55b = 2.4 }}}
(2) {{{ b = 4.364 }}} 
4.4 gallons of mixture should be removed
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check:
{{{ a = .45*4.364 }}}
{{{ a = 1.964 }}}
{{{ ( -1.964 + 4.364 )/4 = .6 }}}
{{{ 2.4002 = 2.4 }}}
error due to rounding off
OK