A guy has a mix of one, five, and ten dollar bills. There are 27 bills in a jar for a total of $91. There are four times as many ones as tens. How many five dollar bills are in the jar?

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?

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 for an uberi is $2.50 plus $2.00 mile. if the total for the uber ride was $32.50, how many miles did the customer travel?