What is the quick way to add or subtract simple fractions? Please show an example.

How many days was the temperature above 90 degrees?

David must install fencing around a lot that is shaped like a right angle.the side of lot that runs east-west is 200 ft long.the side of the lot runs north-south is 125 ft long.calculate how many feet of fencing he will need to surround the entire lot.

What is the ratio for the surface areas of the cones shown below, given that they are similar and that the ratio of their radil and altitudes is 4: 3? 23