Hello, cassiopeia1289!
Bank ID number is: . and has an illegible 4th digit.
Determine the value of
They also give the check-digit formula:
. .
Using the check-digit formula:
. .
. .
We have: .
. . . . . . . .
. . . . . . . . .
Bank ID number is 237(a4)18538 and has an illegible 4th digit.
Determine the value of a4.
They also give the check digit formula, so a9 = 7(a1) + 3(a2) + 9(a3) + 7(a4) + 3(a5) + 9(a6) + 7(a7) + 3(a8) (mod 10)