Answer :
there are 3 different numbers
slot method
how many 3 digit numbers?
321
312
123
132
213
231
6 numbes
how many 2 digit numbers?
12
21
13
31
23
32
6 numbers
how many 1 digit numbers
1
2
3
3 of them
6+6+3=15
15 different number, yah you ar right
slot method
how many 3 digit numbers?
321
312
123
132
213
231
6 numbes
how many 2 digit numbers?
12
21
13
31
23
32
6 numbers
how many 1 digit numbers
1
2
3
3 of them
6+6+3=15
15 different number, yah you ar right