Algebraic puzzle (money comparison and trebling): Determine the boys' original combined amount. Mac initially has £3 more than Ken. Ken then trebles his money and ends up with £2 more than the original combined total. Find the amount the two boys had between them before Ken's win. Choose the correct value.

Let Ken = k, Mac = k + 3. Original total T = 2k + 3.

Condition after winning Ken trebles his money ⇒ new Ken = 3k. Given: 3k = T + 2 = (2k + 3) + 2 = 2k + 5.

Solve 3k = 2k + 5 ⇒ k = 5. Original total T = 2k + 3 = 10 + 3 = £ 13.

Common pitfalls Adding the £2 to Ken's old amount instead of to the original combined total.