How are predicting outcomes based on theoretical probability and on experimental probability the same and different?

What is the inverse of the function f(x)=4x+8

One of every 20 customers reports poor customer service on your company’s customer satisfaction survey. you have just created a new process that should cut the number of poor customer service complaints in half. what percentage of customers would you expect to report poor service after this process is implemented? 1.) 5% 2.) 10% 3.) 2% 4.) 2.5%

2x minus y equals 6, x plus y equals negative 3