Question 1032946
Let {{{ a }}} = Jean's age now
Let {{{ b }}} = her sister's age now
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(1) {{{ a = 3b }}}
(2) {{{ a + 6 = 2*( b + 6 ) }}}
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Substitute (1) into (2)
(2) {{{ 3b + 6 = 2*( b + 6 ) }}}
(2) {{{ 3b + 6 = 2b + 12 }}}
(2) {{{ b = 6 }}}
and
(1) {{{ a = 3b }}}
(1) {{{ a = 3*6 }}}
(1) {{{ a = 18 }}}
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Jean is 18
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check:
(2) {{{ a + 6 = 2*( b + 6 ) }}}
(2) {{{ 18 + 6 = 2*( 6 + 6 ) }}}
(2) {{{ 24 = 2*12 }}}
(2) {{{ 24 = 24 }}}
OK