Trina read 1/2 of a book in the morning, and she read some more at night. By the end of the day, she still had 2/5 of the book left to read. How much of the book did Trina read at night?

Afarmer has a large field that is x feet in length. he wants to fence in a rectangular section in the middle of the field , leaving a length of 100 feet of open field behind each end of the fenced rectangle.he also wants the width of the fenced-in space to be 100 feet less than its length. find the expressions to represent the length and width of the fenced section of the field