Question

id="TexFormula1" title="\pi7^{2} \times 28 - \pi2.25 {}^{2} \times 28" alt="\pi7^{2} \times 28 - \pi2.25 {}^{2} \times 28" align="absmiddle" class="latex-formula">

Answer 1

I don't see any relationship between the expression you have shared and the volume of paper towels.

If you wish to simplify  the given expression, factor out 28, obtaining 
28*pi(49 - 5.0625) = 28*pi*(43.9375).

You could leave your answer as shown, or you could multiply it out.  Try several forms of presentation.  Which one is closest to the answer to this problem?