In A School Band 9 Kids Play String Instruments 10 Kids Play Woodwind Instrument

 In a school band, 9 kids play string instruments, 10 kids play woodwind instruments, 7 kids play brass instruments, and 4 kids play percussion instruments.

a.    What is the probability that you randomly select a kid who plays a string or percussion instrument?

b.    What is the probability that you randomly select a kid who does not play a brass instrument?