The circle expands it radius 20m each day. From this description you can get this equation:
r=0+ 20*d
r=20d
The oil slick expands as a circle and the formula for circle area is

r^2. If you insert the first equation into this equation you will got:
circle area =

r^2
circle area =

(20d)^2
circle area =

400*d^2
Answer: 22 ft²
Step-by-step explanation:
To find the area of a rectangle, we multiply the length and width. It doesn't matter which is which as we get the same answer in the end.
Given information:
Length = 11 ft
Width = 2 ft
Area = length x width
Area = 11 ft x 2 ft = 22 ft²
You'll notice the unit is feet squared or ft², because feet x feet gives us feet².
1st equation x - 7 < 14:
x < 14 + 7 (add 7 to both sides)
x < 21 (add 14 + 7 so it can equal 21)
2nd equation x + 13 > 21:
x > 21 - 13 (subtract 13 from both sides)
x > 8 (subtract 21 - 13 so it can equal 8)