Juan builds a square dog pen that has an area of 100 square feet. He then builds a second pen that has an area of 49 square feet. Which is the closest to the percent of the decrease in the area of the pen? * IT IS NOT 221

Jeffery conducted a survey in his school and found that 30 of the 50 eighth grade students' favorite subject is mathematics. based on the results, jeffery concluded that out of the 200 students in his school, 120 students' favorite subject is mathematics. select the statement that is true about jeffery's conclusion. a. jeffery's conclusion is not valid because the sample was biased since only 200 students were surveyed. b. jeffery's conclusion is valid because the sample was random since all of the students were eighth grade students. c. jeffery's conclusion is valid because the sample was random. d. jeffery's conclusion is not valid because the sample was biased since all of the students were eighth grade students.

Can someone me and do the problem plz so i can understand it more better

Ill mark the brainliest if you me with the these three questions 7,8,9