After adding the numbers together you want your total to be divisible by 10.
We have : 8+9+0+1 + 0+9+8+7 + 1+4+3+0+1 + 1+6+7+2+x= 67
Now take the total mod 10.
We have 67mod10
We have : 8+9+0+1 + 0+9+8+7 + 1+4+3+0+1 + 1+6+7+2+x= 67
Now take the total mod 10.
We have 67mod10