The strings cost $14. you would take the total cost ($72) and subtract the cost of the book ($16) and you would get $56. you would then divide 56 by the number of book bought (4 in all) and you would get $14.
C r = (n!)/(r!(n-r)!)
9 C 3 = (9!)/(3!*(9-3)!)
9 C 3 = (9!)/(3!*6!)
9 C 3 = (9*8*7*6!)/(3!*6!)
9 C 3 = (9*8*7)/(3!)
9 C 3 = (9*8*7)/(3*2*1)
9 C 3 = (504)/(6) 9 C 3 = 84
Answer:79
Step-by-step explanation:78: I love the noise
