The length of a rectangular deck is 4 times its width. if the deck's perimeter is 30 feet, what is the deck's area?

36 square feet because the width would be a and so since the length is 4 times that you can say that the two sides added together would be 5a
30 feet is the parameter which would include all 4 sides but we are only looking for 2 sides so you can divide that by 2 so 
5a=15       so divide 15 by 5 and you get 3 so a=3
4a=4*3= 12=length
a=3=width
length*width=area
12*3= 36 square feet

Exponential function