DUE IN A HALF HOUR! HELP QUICK!

Based on what i know about mean, this doesn't add up.

Iwill give brainliest only if your correct the words subsequent and submerge both contain the prefix sub. based on this information, what does the prefix sub most likely mean? a) under or secondary b) true or verifiable c) tricky or difficult d) around or centered on

Layla answer 21 of the 25 questions on his history test correctly.what decimal represents the fraction of problem he answer incorrectly.