Question 872637
Let {{{ b }}} = brother's age now
Let {{{ s }}} = sister's age now
{{{ b - 3 }}} = brother's age 3 yrs ago
{{{ s - 3 }}} = sister's age 3 yrs ago
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(1) {{{ b = 2s }}}
(2) {{{ b - 3 = 3*( s - 3 ) }}}
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(2) {{{ b - 3 = 3s - 9 }}}
(2) {{{ 3s - b = 6 }}}
Substitute (1) into (2)
(2) {{{ 3s - 2s = 6 }}}
(2) {{{ s = 6 }}}
and, since
(1) {{{ b = 2s }}}
(1) {{{ b = 2*6 }}}
(1) {{{ b = 12 }}}
Brother is 12 and sister is 6
check:
(2) {{{ b - 3 = 3*( s - 3 ) }}}
(2) {{{ 12 - 3 = 3*( 6 - 3 ) }}}
(2) {{{ 9 = 3*3 }}}
(2) {{{ 9 = 9 }}}
OK