Your are on a roller coaster that begin 1/5 mile above ground. The roller coaster descends 1/2 mile. What is the roller coatser new location after descending

Can someone me out here number 4 plz

Cody was 165cm tall on the first day of school this year, which was 10% taller than he was on the first day of school last year.

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?