I do not get this question: 6b-5b+(-8b)=?

What is the maximum total area that 450cm of string can enclose if it is used to form perimeters of two adjoining rectangles as shown?

How many days was the temperature above 90 degrees?

() at a farm, animals are fed bales of hay and buckets of gain.each bale of hay is in the shape of a rectangular prism.the base side lengths 2 feet and 3 feet,and the height is 5 feet. each bucket of grain is a cylinder with diameter of 3 feet. the height of the bucket is 5 feet as the height of bale. a. which is larger in area, the rectangular base of the bale or the circular base of the bucket? explain how you know b. which is larger in volume, the bale or the bucket? explain how you know