What is the multiplicative inverse of 13 in mod 15?

The multiplicative inverse of a number "a" modulo "n" is a number "b" such that the product of "a" and "b" is congruent to 1 modulo "n". In other words, (a*b) mod n = 1.

To find the multiplicative inverse of 13 mod 15, we need to find a number that, when multiplied by 13, gives a result that is 1 mod 15.

We can find this by trial and error, or by using the Extended Euclidean Algorithm. In this case, trial and error is faster:

13 * 1 mod 15 = 13 13 * 2 mod 15 = 11 13 * 3 mod 15 = 9 13 * 4 mod 15 = 7 13 * 5 mod 15 = 5 13 * 6 mod 15 = 3 13 * 7 mod 15 = 1

So, the multiplicative inverse of 13 mod 15 is 7, because 13 * 7 mod 15 = 1.