Answer:
multiply pi (3.14) by 2 and that would give it to you.
Step-by-step explanation:
Given the equation of a circle in the form

You have that
is the center, and
is the radius.
So, in your case, the center is
and the radius is 5.
You basically would just divide, $24.18 by 3 . since they split the cost.
1.37x + 1.08y = 16.36
x + y = 13
x = 13 - y
1.37* (13-y) + 1.08y = 16.36
17.81 - 1.37y + 1.08y = 16.36
1.08y - 1.37y = 16.36 - 17.81
-0.29y = -1.45
y = 5
x + 5 = 13
x = 13-5
x = 8
He bought 8 notebooks and 5 book covers