Find the number of combinations of 7 objects taking 2 at a time. A class has 14 boys and 16 girls. The class has to elect one boy and one girl to be representatives on a committee. A license plate has 3 letters and 3 digits in that order. A witness to a hit and run accident saw the first 2 letters and the last digit.
Permutations are when order is important.
Combinations are when order is not important.