I would say that while these answers are perfectly correct. I think that we want to use logic and reasoning to solve these problems as well and there is nothing wrong with using some estimation or "guess and check" when presented with these problems.
First of all, we should realize that the sum of the ages is 30, so there is no possible way that either answer could be over 30. I have seen many students come up with what they think is the correct "formula" only to follow it and arrive at an answer that makes absolutely no sense. They then write this answer on a test because it is the answer their incorrect formula led them to....
Next, we know that Jan is three year's less than twice Tritt's age. Again, Jan cannot be older than Tritt, can he?
*** A common error here would be to say that Jan is 14 and Tritt is 17 as they are three years apart, but this does not account for the "twice" condition. Twice is simply a vocabulary term that you must know means double or two times something. If you don't realize this try to put twice in a sentence and then evaluate it mathematically. I.e., I have twice as many marbles as my sister. If she has four, how many do I have?, etc...
The same applies to less than, which is a commonly misunderstood phrase....***
So, if it is 3 less than two times as many as Tritt you can start guessing and checking at Tritt's age... 8? If it were 8 you would need two times 8 which is 16 and then 3 less than that is 13. 16 plus 13 make 39, which is too big so I would try a smaller number, etc...
