We'll assume that you only want to talk about whole numbers.
The smallest 7-digit number is 1,000,000. The largest one is 9,999,999.
They represent (all of the counting numbers up to 9,999,999) minus (the first 999,999).
That leaves 9,000,000 numbers
Since the numbers begin with 123, they all contain a 3. As a result, they all "contain 3 or 7". So the remaining 4 digits can be any digits and this gives 104 = 10,000 such numbers.
A crore has 7 digits.
7
180
There are 192.
Since the numbers begin with 123, they all contain a 3. As a result, they all "contain 3 or 7". So the remaining 4 digits can be any digits and this gives 104 = 10,000 such numbers.
A crore has 7 digits.
7
36 of them.
There are 13 such numbers.
8.
180
There are 192.
120 There are 6 digits in total. The numbers with 3 digits, with all digits distinct from each other, are the permutations of the 6 digits taken 3 at a time, and therefore there are 6*5*4 = 120 of them.
7 two-digit numbers.
252 of them.
5,050