The area of a rectangular ice skating rink is 900 square yards if the length of the rink is 100 yards what is the width of the rink ?

Well to find the area of a rectangle you have to go length times width.
If the area is 900 and the length is 100. You already have a basic equation.

100 times X = 900.
X will equal the width.

To get the answer, you have to reverse this equation so you divide the area by the length.

900 divided by 100. That comes to 9.
The width of the rectangle is 9. Hope this helped!:)