What is the answer to my problem

The sixth grade art students are making a mosaic using tiles in the shape of right triangles. each tile has leg measures of 3 centimeters and 5 centimeters. i f there are 200 tiles in the mosaic what is the area of the mosaic.

Turner's mom measured his room to see how long the wallpaper border needed to be. if two walls are 15 feet long and two walls are 12 feet long, how long should the strip of border be cut?

How are algebraic expressions evaluated using substitution?