This question might sound a little silly, but I was not able to figure the solution to this.

Say, I want to compute an expression of the form (a * b) / c, and I want to do it modulo 13. Now, if a = 13, b = 3, c = 13, then the answer clearly is 3. But if I try to do it this way (((a % 13) * (b % 13)) * inv(c % 13)) % 13, where inv(x) return the multiplicative inverse of x modulo 13, it will not work out. So, how to work around this one ?