Find the missing digit:
0-875?7-79000-7
0x3+8+7x3+5+Nx3+7+7x3+9+0x3+0+0x3+7=0
8+21+5+Nx3+7+21+9+7=0
78+Nx3=0
8+Nx3=0
Nx3=0-8=2
We need Nx3=2, 12 or 22
4x3=12
N=4