Math problem i have: if the sales tax for the city of los angeles is 9.75%, how much tax would you pay for an item that costs $200?

Margie is practicing for an upcoming tennis tournament. her first serve is good 20 out of 30 times on average. margie wants to know the estimated probability that her first serve will be good at least four of the next six times she serves. how could she design a simulation for this scenario?