Question 665558
Let {{{ f }}} = Father's age now
Let {{{ s }}} = Son's age now
{{{ f - 7 }}} = Father's age 7 yrs ago
{{{ s - 7 }}} = Son's age 7 yrs ago
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given:
(1) {{{ f = 4s }}}
(2) {{{ f - 7 = 11*( s - 7 ) }}}
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(2) {{{ f - 7 = 11s - 77 }}}
(2) {{{ f = 11s -70 }}}
Substitute (1) into (2)
(2) {{{ 4s = 11s -70 }}}
(2) {{{ 7s = 70 }}}
(2) {{{ s = 10 }}}
and, since
(1) {{{ f = 4s }}}
(1) {{{ f = 4*10 }}}
(1) {{{ f = 40 }}}
The father is 40 and the Son is 10
check answer:
(2) {{{ f - 7 = 11*( s - 7 ) }}}
(2) {{{ 40 - 7 = 11*( 10 - 7 ) }}}
(2) {{{ 33 = 11*3 }}}
(2) {{{ 33 = 33 }}}
OK