Please help me with this question please?

How many different ways can you make change for $.50 using only nickels,dimes, and quarters?

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

Me! i will mark you brainliest if you are right and show your i don't get polynomials and all the other stuff. multiply and simplify.2x(^2)y(^3)z(^2) · 4xy(^4)x(^2)show your