Question 1096774
You have to read it pretty carefully.
I'm assuming that Mary is Olan's sister.
Let {{{ a }}} = Olan's age now
Let {{{ b }}} = Mary's age now
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(1) {{{ a = b + 3 }}}
(2) {{{ (1/3)*a = (1/2)*( b - 1 ) - 2 }}}
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Note that {{{ b - 1 }}} is Mary's age 1 year ago 
(2) {{{ (1/3)*a = (1/2)*b - 1/2 - 4/2 }}}
(2) {{{ (1/3)*a = (1/2)*b - 5/2 }}}
Multiply both sides by {{{ 6 }}}
(2) {{{ 2a = 3b - 15 }}}
(2) {{{ -2a + 3b = 15 }}}
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(1) {{{ a - b = 3 }}}
Multiply both sides of (1) by {{{ 2 }}}
and add the equations
(1) {{{ 2a - 2b = 6 }}}
(2) {{{ -2a + 3b = 15 }}}
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{{{ b = 21 }}}
and
(1) {{{ a = b + 3 }}}
(1) {{{ a = 21 + 3 }}}
(1) {{{ a = 24 }}}
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Olan is 24
Mary is 21
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check:
(2) {{{ (1/3)*a = (1/2)*( b - 1 ) - 2 }}}
(2) {{{ (1/3)*24 = (1/2)*( 21 - 1 ) - 2 }}}
(2) {{{ 8 = (1/2)*20 - 2 }}}
(2) {{{ 8 = 10 - 2 }}}
(2) {{{ 8 = 8 }}}
OK