Why do my work seem easy but i messed up but i dont see where wit these tricky variables

Which representation has a constant of variation of -2.5

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

Venita is sewing new curtains. the table below shows the relationship between the number of stitches in a row and the length ofthe row.sewingnumber of stitches length (cm)51 131532024306what is the relationship between the number of stitches and the length? othe number of stitches istimes the length.o. the number of stitches is 3 times the length.