One painter can finish a certain job 5 hours before another painter who is doing the same job. when they work together they can finish this job in 6 hours. how long does it take for each painter to do the job by himself?

The salesperson earns a 5% commission on the first $5,000 she has in sales. the salesperson earns a 7.5% commission on the amount of her sales that are greater than $5,000. this month the sales person had $8,000 in sales. what amount of commission, in dollars, did she earn?