A doctor conducts an experiment to test new treatments for a medical condition. Of the 16 volunteers in the experiment, 4 do not receive any treatment. What percent of the volunteers do not receive any treatment? PLZ HELP MEH!!! :)

12, cause there are 16 volunteers and 4 do not receive treatment so 16-4=12

To solve this problem, we first need to find each of their hourly rates. We can do this by dividing the boxes by the number of hours. Using this method, we get that Jack wraps 14 boxes per hour and Walter wraps 12 boxes per hour. So, since the question has them working together, the rate is the sum of each of their individual rates per hour. Since we know that they work for t hours, we can multiply their combined rate by t (since in a job problem, job = time * rate). And, on the other end of the equal sign, since we know that they wrapped 65 presents, we put 65 there. The equation becomes:

(14+12)t = 65

Which simplifies to 
26t = 65