Is a biased sample (always, sometimes, or never true) valid and why?

Which expression do you get when you eliminate the negative exponents of 4a^2 b^216a^-3 b

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?

Ten members of balin's soccer team ran warm ups for practice. each member ran the same distance. their combined distance was 5/6 of a mile. to find the distance that each member ran, balin wrote the expression below.