If the original quantity is 20 and the new quantity is 18 what is the percent decrease

Mr switzer needs to buy new 1-foot tiles to cover his bathroom floor. the floor is 12 feet long and 8 feet wide. each square foot of tile will cost $1.79. in dollars what will be the total cost of the tiles he needs to buy.

In the given figure ar(adf) =ar(cda) and ar(cdf) = ar(cdf). show that abdc and cdfe are trapeziums.

What is the slope of the line shown below?