Question 899973
Let {{{ x }}} = amount invested @ 10%
Let {{{ y }}} = amount invested @ 2%
{{{ y }}} = amount invested @ 40%
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(1) {{{ x + 2y = 20000 }}}
and
(2) {{{ .1x + .02y + .4*y = 3320 }}}
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(2) {{{ .1x + .42y = 3320 }}}
(2) {{{ 10x + 42y = 332000 }}}
(2) {{{ 5x + 21y = 166000 }}}
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Multiply both sides of (1) by {{{ 5 }}}
and subtract (1) from (2)
(2) {{{ 5x + 21y = 166000 }}}
(1) {{{ -5x - 10y = -100000 }}}
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{{{ 11y = 66000 }}}
{{{ y = 6000 }}}
and, since
(1) {{{ x + 2y = 20000 }}}
(1) {{{ x + 2*6000 = 20000 }}}
(1) {{{ x = 20000 - 12000 }}}
(1) {{{ x = 8000 }}}
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The amount invested @ 10% is $8,000
The amount invested @ 2% is $6,000
The amount invested @ 40% is $6,000
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check:
(2) {{{ .1x + .02y + .4*y = 3320 }}}
(2) {{{ .1*8000 + .02*6000 + .4*6000 = 3320 }}} 
(2) {{{ 800 + 120 + 2400 = 3320 }}}
(2) {{{ 3320 = 3320 }}}
OK