A trick that is good for multiplying 9's is, remember that each time the tens digit changes the number in the ones spaces minuses 1. If you don't understand what I am saying look at the following:-
9
18
27
36
45
54
63
72
81
See the pattern? In the tens place you need to add 1 and in the tens place you need to subtract by 1.
Hope I helped ya!! xD