13. at a certain laboratory, chemical substances are identified by an unordered combination of 3 colors. if no chemical may be assigned the same colors, what is the maximum number of substances that can be identified using 7 colors?

Desmond wants to sell his car that he paid $8,000 for 2 years ago. the car depreciated, or decreased in value, at a constant rate each month over a 2-year period. if x represents the monthly depreciation amount, which expression shows how much desmond can sell his car for today? \ 8,000 + 24x 8,000 - 24x 8,000 + 2x 8,000 - 2x