According to all great mathematicians of all times....all the constintanious experts....all of them say that the only way of making math easy is by practice
eventhough there are some tips the actual method is practice
1.when adding many large no.s divide them into sections of thousand hundred etc.
finally sum up all the sections
2.when doing multiplication of nos with many zeros multiply the non zero nos in the end and then add the zeros to the product