The low temperatures for Anchorage, Alaska last week were: -17°F, 8°F, -9°F, -11°F, 12°F, -13°F, and 2°F. What was the average low temperature for the week?

Ineed i been stuck on this question since yesterday

Can someone factor this fully? my friend and i have two different answers and i would like to know if either of them is right. you in advance. a^2 - b^2 + 25 + 10a

He ! a group of farmers planned to clean 80 acres of wheat per day to finish the work on schedule. right before the work started, they received a new piece of machinery that them clean 10 more acres per day than originally planned. as a result of increased productivity in the last day before the deadline they only had to clean 30 acres. how many acres of wheat did the group of farmers have to clean?