Stephanie has $152 in her bank account. she withdraws $20. then, she deposits $84. write an addition expression to represent this situation. then, find the sum and explain it's meaning.

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.

How do i simply this expression (quadratic formula basis) on a ti-84 or normal calculator?

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'