The first one: the number has to be greater than 23000. So the number at ten thousand place can be occupied by any one of the numbers, 2,3,4,5,6 That is in 5 ways.

number at thousand place can be occupied by any one of the digits 3,4,5,6, that is in 4 ways The number at hundred place can be any one of the remaining 4 digits and tens place can be filled by any one of the remaining 3 digits and units place by remaining 2 numbers.

So we have total numbers greater than 23000 is given by 5x4x4x3x2