To do addition fastly learn these these might be there in some of the tables book-
and so on or if you get 2+2+2+2+2+2
instead of calculating one by one you vcan do like-2 multiplyed by 6 that is 2 being multiplied six times
try remebering the ones given at the first i do it i that way the way avini said is also good but if you remember like 9+9=18 and so on it will be easy at first you will get bored but just read it like tables every morning read it twice and then in one week you will be a genius . hope you like it !!!!!!!