if N is divisible by 2 but not by 3 then what is the remainder when N is divided by 6

N is an even number. Since it is not divisible by 3, it can be of the form 3k + 1 or 3k + 2
Even natural numbers that are in 3k+1 category are 4, 10, 16,... The remainder when these numbers are divided by 6 is 4.
Even natural numbers that are in 3k+2 category are 8, 14, 20,... The remainder when these numbers are divided by 6 is 2.
So, the remainder can be either 2 or 4.

2

2

the remainder can be either 2 or 4

2