If your only option is to assemble the digits into a single number, then the answer is 0, as you need at least one even digit to make an even number, and the digits provided are all odd ones.
If on the other hand, you can use operators on them (e.g. 1 + 3 + 5 + 7), then you actually have quite a large number of possibilities. For example:
1 + 3 + 5 + 7
- 1 + 3 + 5 + 7
1 - 3 + 5 + 7
(1 + 3) / ( 7 - 5)
1 + √(7 + 5 - 3)
31 + 57
etc. etc.
Alternatively, if you're not worried about them being even numbers, then the answer is 24.
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.
There are 900 three-digit numbers, ranging from 100 to 999.
27 three digit numbers from the digits 3, 5, 7 including repetitions.
500
24
840
There are 60480 numbers.
180 of them.
There are 3024 of them.
1 set
It is 120 if the digits cannot be repeated.
There are 5! = 120 such numbers.