Question 669061
Let {{{ b }}} = Ben's age now
Let {{{ r }}} = Robin's age now
{{{ r - 1 }}} = Robin's age 1 year ago
{{{ r - 1 + 10 }}} = 10 greater than Robin's age 1 year ago
given:
(1) {{{ b = 2r }}}
(2) {{{ b = r - 1 + 10 }}}
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Substitute (1) into (2)
(2) {{{ 2r = r - 1 + 10 }}}
(2) {{{ r = 9 }}}
and
(1) {{{ b = 2r }}}
(1) {{{ b = 18 }}}
Ben is 18