Question 736021
Let {{{ j }}} = Judy's age now
Let {{{ n }}} = niece's age now
given:
(1) {{{ j = 3n }}}
(2) {{{ j - 7 = 5*( n - 7 ) }}}
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(2) {{{ j - 7 = 5n - 35 }}}
(2) {{{ j = 5n - 28 }}}
Substitute (1) into (2)
(2) {{{ 3n = 5n - 28 }}}
(2) {{{ 2n = 28 }}}
(2) {{{ n = 14 }}}
and
(1) {{{ j = 3*14 }}}
(1) {{{ j = 42 }}}
Judy is 42
Jill is 14
check:
(2) {{{ j - 7 = 5*( n - 7 ) }}}
(2) {{{ 42 - 7 = 5*( 14 - 7 ) }}}
(2) {{{ 35 = 5*7 }}}
(2) {{{ 35 = 35 }}}
OK