The diagonal entries are void because we cannot pick two tags with the same number. We count 72 outcomes (excluding diagonal) and 12 of them are threes. Therefore Probability that the difference is 3 = 12/72 = 1/6
This is the concept of arithmetic, if you increase your score of 85% by 7%, you will have a score of: New score=old score+increase =85+7 =92% the new score will be 92%