This is because if 3 plus 3 is 6 then you multiply 28 times 2 and you get 56 because 3 can go into 6 2 times if you understand what I mean but the answer is 56 minutes.
The first row is 15,so you have to add three from the first row you and you get 18 and then you keep going and going till you get to the 17th row then you add the numbers together.
