Question 1050212
Let {{{ a }}} = Sally's age now
Let {{{ b }}} = Joe's age now
Let {{{ c }}} = Chris's age now
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(1) {{{ a = 3b + 1 }}}
(2) {{{ c = 6b - 5 }}}
(3) {{{ a = c }}}
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Substitute (3) into (2)
(2) {{{ a = 6b - 5 }}}
(2) {{{ -a + 6b = 5 }}}
and
(1) {{{ a - 3b = 1 }}}
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Add (1) and (2)
(1) {{{ a - 3b = 1 }}}
(2) {{{ -a + 6b = 5 }}}
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{{{ 3b = 6 }}}
{{{ b = 2 }}}
and
(1) {{{ a = 3b + 1 }}}
(1) {{{ a = 3*2 + 1 }}}
(1) {{{ a = 7 }}}
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(3) {{{ a = c }}}
(3) {{{ 7 = c }}}
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Sally is 7
Joe is 2
Chris is 7