Cathy earns $13.50 per hour for the first 40 hours worked in a week and $20.25 per hour for hours over 40. if she earns $661.50 one week. how many hours does she work? show your work using a variable that represents a time, in hours, that cathy works over 40 hours.

Suppose that 3% of all athletes are using the endurance-enhancing hormone epo (you should be able to simply compute the percentage of all athletes that are not using epo). for our purposes, a “positive” test result is one that indicates presence of epo in an athlete’s bloodstream. the probability of a positive result, given the presence of epo is .99. the probability of a negative result, when epo is not present, is .90. what is the probability that a randomly selected athlete tests positive for epo? 0.0297

Mat bought a phone for $100. he has to pay $30 per mouth. if he has paid $640 in total, how many mouth has he had the phone?

What is negative 3/9 times negative 2/8 ?