Which equation represents an empty set? x2+4x+4=−y2 −15=−x2−y2−4x 1+x2−2x=−y2+8y−22 −21+x2+y2+4x=0

Ineed with math stuff it involves graphs

Can you me with this question? i'll reward *30 points i just need with this one question so that i could solve the others. * edit: i originally set up the question to reward 30 points, but for some reason i can only reward 15. if you don't get 30, then i'm sorry. i'm still kind of new to this site

The line plot below represents the number of letters written to overseas pen pals by the students at the waverly middle school.each x represents 10 students. how many students wrote more than 6 and fewer than 20 letters. a.250 b.240 c.230 d.220