Find the number of four-digit numbers which are not divisible by 4?
There are 9 choices for the first (left-hand) digit and 10 choices for the second digit, giving 9 x 10 = 90
choices for the first two digits.
The last two digits, starting with 00 must be divisible by 4; such as 00, 04, 08, 12, etc.
How many choices are there for the last two digits?
Multiply this answer by 90 to get the final answer for the number of numbers that are divisible by 4.
To find the number that are divisible by 4, subtract that answer from 9999.