a) P7 / P5 = 7! / 5! = (5!*6*7)/5! = 6*7 = 42
b) P3 = 3! = 1*2*3 = 6
A₅² = 5! /(5-2)! = 5! / 3! = (3!*4*5)/ 3! = 20
C₅³ = 5! / (3!*2!) = (3!*4*5) / (3!*2) = 2*5 = 10
6+20+10 = 36
