There will be 18 exterior angles, each of 360/18 = 20 deg. So each interior angle, which is supplementary to the exterior angle will be 180–20 - 160 deg. The sum of the 18 interior angles = 18*160 = 2880 deg.
The formula for volume of a sphere is

To get radius from diameter, we must divide it by 2. 10/2=5, meaning the radius is 5 in.
Now, we just need to plug the values into the equation.
First convert 22 to decimal form. You do this by dividing the percent by 100.
22 / 100 = .22
Then multiply the dollar amount by the percentage in decimal form.
$45 * .22 = $9.9
So 22% of $45 is $9.9.
Then you subtract $9.9 from $45.
$45 - $9.9 = $35.1
Okay. So, she buoyant 5.65 lbs of roast beef for $4.50. Multiply both of those numbers to get 25.425 or 25.43 when rounded to the nearest hundredth. So the total cost was $25.43. However, we now have to divide the amount by 6.5. 25.43/6.5 is 3.912 and other odd numbers or 3.91 when rounded to the nearest hundredth. The cost per sandwich was $3.91.