Question 1128905
Let {{{ a }}} = John's age now
Let {{{ b }}} = Peter's age now
Let {{{ c }}} = Alice's age now
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(1) {{{ a = 2b }}}
(2) {{{ b = c + 5 }}}
(3) {{{ a + 5 = 3*( c + 5 ) }}}
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(2) {{{ c = b - 5 }}}
Plug (1) and (2) into (3)
(3) {{{ 2b + 5 = 3*( b - 5 + 5 ) }}}
(3) {{{ 2b + 5 = 3b }}}
(3) {{{ b = 5 }}}
and
(2) {{{ c = 5 - 5 }}}
(2) {{{ c = 0 }}}
and
(1) {{{ a = 2b }}}
(1) {{{ a = 10 }}}
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Peter is 5 now
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check:
(1) {{{ 10 = 2*5 }}}
(2) {{{ 5 = 0 + 5 }}}
(3) {{{ 10 + 5 = 3*( 0 + 5 ) }}}
(3) {{{ 15 = 15 }}}
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Note that Alice is newborn now
check the math