Jim bought some chocolates and gave half of it to Ken. Ken bought some sweets and gave half of it to Jim. Jim ate 12 sweets and Ken ate 18 chocolates. The ratio of Jim’s sweets to chocolates became 1:7 and the ratio of Ken’s sweets to chocolates became 1:4. How many sweets did Ken buy?

I really think this question is tough, and is the type which I will skip upon finish reading.

It's only a PSLE (Primary School Leaving Examination) question and I can't even answer ):

How can you expect the students themselves to answer?

Perhaps I'm just too rusty for this kind of thing already..