Question 424031
Let {{{a}}} = Adam's age now
Let {{{f}}} = Frank's age now
given:
(1) {{{f = (2/3)*a}}}
(2) {{{ f + 7 = (3/4)*(a + 7) }}}
--------------------
(2) {{{ 4f + 28 = 3*(a + 7) }}}
(2) {{{ 4f + 28 = 3a + 21 }}}
(2) {{{ 4f = 3a - 7 }}}
Substitute (1) in (2)
(2) {{{ 4*(2/3)*a = 3a - 7 }}}
(2) {{{ 8a = 9a - 21 }}}
(2) {{{ a = 21 }}}
and
(1) {{{ f = (2/3)*21 }}}
(1) {{{ f = 14 }}}
Adam is 21 now and Frank is 14 now
check:
(2) {{{ f + 7 = (3/4)*(a + 7) }}}
(2) {{{ 14 + 7 = (3/4)*(21 + 7) }}}
(2) {{{ 21 = (3/4)*28 }}}
(2) {{{ 84 = 84 }}}
OK