12 ? You must be joke . 12 is normal . Should be higher as like this I make today

Easy

Yes , many many times . The key is : after 8 do not just try to get higher number . You have plan and make sure your have next lower number ready .
For example : if you have 9 and 9 : normally you try to get 10 . Do not do it . Prepare you have 9,9 and 8 , 8
Therefore you can get 10 at the same time you can get 9 . Also later combine to higher number that you have higher chance to combine the lower number that you can finally get higher numbers