A sink contains exactly 12 litres of water. If water is drained from the sink until it holds exactly 6 litres of water less than the quantity drained away, then how many litres of water were drained away?
(a)2
(b)3
(c)6
(d)9
Answer
Answer (as printed): D
Explanation
Let the quantity of water drained away be $x$ litres. Then, $12-x=x-6 \Rightarrow 2 x=18 \Rightarrow x=9$.
Explanation as extracted from the printed page; notation may be imperfect.