The lowest common denominator is 340.
If <em>X</em> - <em>A</em> = <em>B</em>, then <em>X</em> = <em>A</em> + <em>B</em>. So

The formula for finding the surface area of a sphere is A=4π

. Since we already have the radius, we just plug that into the equation, like so:
A = 4 x 3.14 x 
First, following the rules of PEMDAS, do the exponent, coming out with an answer of 1. Now, multiply 4 x 3.14, which is 12.56. 12.56 x 1 = 12.56.
Rounded to the nearest tenth, your answer is
12.6.
Hope this helps!
C is incorrect. 8f represents the cost of 8 formulas, not just the cost of one formula.