If by numbers the question means digits then there are 6 ways of combining 4, 6 and 8:
468, 486, 648, 684, 846, 864; but the digits can be combined in pairs: 46, 64, 48, 84, 68, 86.
They can also be combined by inserting operators (+, -, *, ÷) between them. Taking + and - only we have: 4+6+8, 4+6-8, 4-6+8, 4-6-8, 6+4+8, 6+4-8, 6-4+8, 6-4-8, etc. This makes 4 combinations of numbers and signs for each of the 6 combinations of 3 digits, making 24. We can similarly add another 24 using multiply and divide; then 24 combinations for add with multiply; 24 for add with divide; 24 for subtract with multiply; 24 for subtract with divide. In all we have 16*6=96 combinations using 4 operators. We could go on with the pairs using all these operators between the pairs. We also have the exponent operator. That makes 5 operators, introducing a factor of 32 for the combinations in place of 16. For pairs of numbers we can only have one operator between them, so the 6 pair combinations produce 6*5=30 arithmetic results. The sums, differences, products, quotients and exponentials will not necessarily be unique (for example 4+6+8=6+8+4), but that's because of the properties of numbers and rules of arithmetic, rather than arranging the numbers in any sort of order.