One example.
12*8+3+7-6 = 100
The key is finding sets of 10s
3! = 6.
4*3*2 = 24 of them.
5! / 4 - 2 * 3
total 6 they are 3412,4312,1324,3124,1432,4132
None.
5*4+3+2
3! = 6.
4*3*2 = 24 of them.
5! / 4 - 2 * 3
total 6 they are 3412,4312,1324,3124,1432,4132
(4+5-6)x8=24
8
If you want 4-digit numbers, there are 24 of them.
None.
-9
-1230
(3-1) x (2+8)(9-6) Essentially, the above sum is 2x103