Please help! This is 6th grade math

Which expression is equivalent to 8(k + m) − 15(2k + 5m)?

How to do this , and can some one explain

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%