5 + 6 + 4 = 15 total sandwiches.
6 are cheese.
Probability 1st person picks cheese would be 6/15 = 2/5 ( 6 cheese sandwiches over total sandwiches).
After the 1st person takes a sandwich there are 14 left.
5 are turkey.
Probability the 2nd person picks turkey is 5/14 ( 5 turkey sandwiches over total sandwiches left).
The probability of both happening =
2/5 x 5/14 = (2 * 5) / (5 * 14) = 10/70 = 1/7
