You have to be good at visually verifying numbers - i.e. is 23456 the same as 23455 - no. Practice recognizing patterns such as 2, 4, 6, 8 , 10 whats the next number? 12. 1,3,6,10 - next number is 15. If you do not get this then you will be dropped from interview process. Next, just sound super confident as if you already got the job. You always want to thank them at the start of the interview for their time and say something like "Hopefully it warms up soon!"