Answer:
Current age of Monica=6 years
and current age of William=18 years
Explanation:
Let Monica's current age be x years and William's current age be y years.
William is 3 times elder than Monica.
⇒ y=3x
In 6 years William will be twice as old as Monica.
⇒ y+6=2(x+6)
⇒ y+6=2x+12
⇒3x+6=2x+12
⇒ x=6
Hence, y=3×6=18
That means, current age of Monica=6 years
and current age of William=18 years