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put this solution on YOUR website!Let

= A's age now
Let

= B's age now

= A's age 7 years ago

= B's age 7 years ago
---------------------------
given:
7 years ago, A was 3 years younger than B is now
(1)

7 years ago, B was twice as young as A ( half A's age )
(2)

---------------------
(2)

(2)

(2)

and
(1)

(1)

(1)

(1)

Substitute (1) into (2)
(2)

(2)

(2)

(2)

A is 15
check:
(1)

(1)

(1)

(2)

(2)

(2)

(2)

OK