Question 666033
Let {{{ a }}} = Derek's age now
Let {{{ b }}} = Brother's age now
------------
given:
(1) {{{ a = 4b }}}
(2) {{{ a - 5 + b - 5 = a }}}
----------------------
(2) {{{ b - 10 = 0 }}}
(2) {{{ b = 10 }}}
and
(1) {{{ a = 4*10 }}}
(1) {{{ a = 40 }}}
Derek is 40 and his Brother is 10