First 33.25 was divided by some number. the resulting quotient was then multiplied by 7. following this 5.9 was subtracted from the product giving 18.6. What is the initial divisor?

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?