Still noone has told you what to do? The simple and very useful trick? You can do this in Chapter 3, and though Shinra may seem hard, he is possible to beat. Sphere Echoes is the key:

Say there is the number 4 in the centre. 1, 6, 5, 2 are surrounding the centre coin. Then you have the rest of the coins outside them all. You select one main coin, either one of those will do, but to get 4 or a multiple of four, you would have to find the right number.

i.e 1 + 3 = 5
6 + 2 = 8
5 + 3 = 8
2 + 2 = 4

So in that round, you will have chosen 2 coins to get the centre number or a multiple of that number.

Next round comes up, you follow the same thing, and try to get the centre number in 2 coins or get a multiple in coins.

Keep on doing this, and your "Sphere Echoes" will double, if I am right, so the higher the rate at which you use 2 coins, the higher you will be able to reach that goal of completing the match and winning the dressphere.

Watch out for number 1's tho as being your center number - if you keep getting them, your Sphere Echoe count will go down to zero, and you'll have to build it up again.

Well the sphere echoe bonus anyway. Points you have already got won't disappear.

If you get too many ones, restart the game and try again.

~Setzer Gabbiani