Hi there! :)
Answer:

Step-by-step explanation:
Formula for the area of a circle:

Rearrange the equation in terms of "r":
Divide 'π' from both sides:

Take the square root of both sides:

So we need to find the two lines...y=mx+b where m is the slope and b is the y-intercept.
m=(dy/dx)=(7-6)/(3-1)=1/2 so
y=x/2+b, now I'll use (1,6) to solve for b
6=1/2+b, b=5 1/2=11/2 so
y1=(x+11)/2
now the other line...
m=(8-6)/(5-3)=2/2=1
y2=x+b, using point (3,6) we solve for b
6=3+b, b=3 so
y2=x+3
Since this is just two lines they will only intersect at a single point and when they do, y=y so we can say:
x+3=(x+11)/2
2x+6=x+11
x+6=11
x=5, now use either line to solve for the corresponding y value...
y2=x+3 becomes y=5+3=8 so the solution to this system is the point:
(5,8)
The answer is four weeks. Do you want an explanation?