Ok i need help with this math test, the questions are in the links, plss help

Write 17/20 as a decimal and as a percent.

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

The cost of using a service is $0.25 per min. what equation correctly represents the total cost c, in dollars, for d days of use?