With repeats: 8^5 = 32768
Without repeats: 8 x 7 x 6 x 5 x 4 = 6720
500
180 of them.
It is 120 if the digits cannot be repeated.
There are 34 = 81 numbers.
I take it that you want to make three digits numbers with 8,7,3, and 6 without repetition. The first digit cane be selected from among 4 digits, the second from 3 digits, the third digit from 2, hence the number of three digit numbers that can be formed without repetition is 4 x 3 x 2 = 24
5040 different 4 digit numbers can be formed with the digits 123456789. This is assuming that no digits are repeated with each combination.
10,000
36
27 three digit numbers from the digits 3, 5, 7 including repetitions.
24
500
There are 60480 numbers.
840
There are 3024 of them.
180 of them.
If the digits can be used more than once, then 900. If not, then 648.
There are 5*4*3 = 60 such numbers.