Question 993937
Let {{{ j }}} = Jane's age now
Let {{{ s }}} = Sam's age now
(1) {{{ j - 4 = 2*( s - 4 ) }}}
(2) {{{ s + 4 = (3/4)*( j + 4 ) }}}
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(1) {{{ j - 4 = 2s - 8 }}}
(1) {{{ 2s - j = 4 }}}
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(2) {{{ 4s + 16 = 3j + 12 }}}
(2) {{{ -4s + 3j = 4 }}}
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Multiply both sides of (1) by {{{ 3 }}}
and add the equations
(1) {{{ 6s - 3j = 12 }}}
(2) {{{ -4s + 3j = 4 }}}
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{{{ 2s = 16 }}}
{{{ s = 8 }}}
and
(1) {{{ j - 4 = 2*( 8 - 4 ) }}}
(1) {{{ j = 2*4 + 4 }}}
(1) {{{ j = 12 }}}
Jane is 12 now
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check:
4 yrs ago, Jane was 8
4 yrs ago, Sam was 4
Jane was 2X as old
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In 4 yrs, Sam is 12
In 4 yrs, Jane is 16
{{{ (3/4)*16 = 12 }}}
OK