66. We need 12C2, combinations of 12 items taken 2 at a time. We're choosing 2 items out of 12, where order does NOT matter, so we use combinations. nCr = n! / (r!(n-r)!), so 12C2 = 12! / (2! x 10!). This equals (12 x 11) / 2! = (12 x 11) / 2 = 66. So 12C2 = 66.