The biggest 4 digit number that can be made from using the digits of 850236, using a digit at most once, is 8653.
-4790281
Assuming each digit only once: 65432 (and no further mathematical operations).
Oh, dude, the biggest number you can make using the digits 9, 5, and 1 is 951. I mean, unless you want to get all fancy and start multiplying or something, but like, who has time for that? Just stick with 951 and call it a day.
It is: 63,477
8,754,321
8643
531
The biggest 4 digit number that can be made from using the digits of 850236, using a digit at most once, is 8653.
9531
-4790281
3201
9876543210
9+3-1
972.
Using those three digits it is 145.
Assuming each digit only once: 65432 (and no further mathematical operations).