Answer:
So the correct option is First one
i.e 
Step-by-step explanation:
Given:
Area of Shaded part = 9 π square feet
To Find :
Area of Circle = ?
Solution:
90 degree center angle is equivalent to an area of 9 Π square feet
So, 360 degree center is equivalent to area A which is the area of the complete circle.
So the Ratio will be
Setting the given statements in proportion:

On solving we get the required

So the correct option is First one
i.e 
Alternate Method:
Shaded part is of 90°
Area of Shaded part = 9 π square feet
And Full Circle is of 360° that is 4 sector of 90°



So the correct option is First one
i.e 
On solving this we get

Answer: - 3.5, -7/3
Step-by-step explanation:
X=width of the lake
y=length of the lake.
we set out this system of equiations
x*y=9/20
x=y/5
we solve by sustitution method
(y/5)*y=9/20
y²/5=9/20
y²=(5*9)/ 20
y²=2.25
y=√2.25=1.5
x=y/5
x=1.5/5=0.3
Solution:
width of the lake=0.3 miles
lenght of the lake=1.5 miles
Explanation:
Pair 1 is true if Jeff's monthly income is $600/20% = $3,000.
Pair 2 is true if Jeff's monthly income is $1200/10% = $12,000.
Both pairs can be true if Jeff's monthly income increased by a factor of 4 in the 20 years from 1990 to 2010.
Obviously, Jeff spent more on housing in 2010. (Fortunately for Jeff, that larger expenditure was a smaller fraction of his income.)