Question 991042
If I read this right, when it says:
" The sum of THEIR ages will be 58 ", THEIR
means all 3 of them
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Let {{{ j }}} = John's age now
Let {{{ f }}} = His father's age now
Let {{{ s }}} = John's sister's age now
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(1) {{{ f = 5j }}}
(2) {{{ j = 2s }}}
(3) {{{ ( j + 2 ) + ( f + 2 ) + ( s + 2 ) = 58 }}}
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(3) {{{ j + f + s + 6 = 58 }}}
(3) {{{ j + f + s = 52 }}}
and
(2) {{{ s = j/2 }}}
Substitute (1) and (2) into (3)
(3) {{{ j + 5j + j/2 = 52 }}}
(3) {{{ 2j + 10j + j = 104 }}}
(3) {{{ 13j = 104 }}}
(3) {{{ j = 8 }}}
and
(2) {{{ s = j/2 }}}
(2) {{{ s = 4 }}}
and
(1) {{{ f = 5j }}}
(1) {{{ f = 5*8 }}}
(1) {{{ f = 40 }}}
John is 8
John's sister is 4
John's father is 40
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check answer:
(3) {{{ ( j + 2 ) + ( f + 2 ) + ( s + 2 ) = 58 }}}
(3) {{{ ( 8 + 2 ) + ( 40 + 2 ) + ( 4 + 2 ) = 58 }}}
(3) {{{ 10 + 42 + 6 = 58 }}}
(3) {{{ 58 = 58 }}}
OK