Question 465452
Let {{{a}}} = Father's age now
Let {{{b}}} = Son's age now
given:
(1) {{{ a = 5b }}}
(2) {{{ b + 15 = (1/2)*( a + 15 ) }}}
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(2) {{{ 2*(b + 15) = a + 15 }}}
(2) {{{ 2b + 30 = a + 15 }}}
(2) {{{ a - 2b = 15 }}}
Substitute (1) into (2)
(2) {{{ 5b - 2b = 15 }}}
(2) {{{ 3b = 15 }}}
(2) {{{ b = 5 }}}
and
(1) {{{ a = 5b }}}
(1) {{{ a = 25 }}}
25 is the Father's age now
5 is the Son's age now
check:
(2) {{{ b + 15 = (1/2)*( a + 15 ) }}}
(2) {{{ 5 + 15 = (1/2)*( 25 + 15 ) }}}
(2) {{{ 20 = (1/2)*40 }}}
(2) {{{ 40 = 40 }}}
OK