Find the mean of the data in the dot plot pls help

How do you use the additive inverse to evaluate an expression that uses subtraction in a full sentence

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

When a valve is open 281 gallons of water go through it in one hour the number of gallons that would go through in 94 hours is