It should be 84500000 centimeters.
x = original price, or 100%
if we take off 25% from 100% what's left is 75%, that's the discounted price.
let's then take 10% of that.
![\bf \begin{array}{|c|ll} \cline{1-1} \textit{a\% of b}\\ \cline{1-1} \\ \left( \cfrac{a}{100} \right)\cdot b \\\\ \cline{1-1} \end{array}~\hspace{5em}\stackrel{\textit{75\% of "x"}}{\left( \cfrac{75}{100} \right)x\implies 0.75x} \\\\[-0.35em] ~\dotfill\\\\ \stackrel{\textit{10\% of 0.75x}}{\left( \cfrac{10}{100} \right)0.75x\implies 0.075x}~\hfill \stackrel{\textit{total percent savings}}{0.75x-0.075x\implies 0.675x} \\\\[-0.35em] ~\dotfill](https://tex.z-dn.net/?f=%5Cbf%20%5Cbegin%7Barray%7D%7B%7Cc%7Cll%7D%20%5Ccline%7B1-1%7D%20%5Ctextit%7Ba%5C%25%20of%20b%7D%5C%5C%20%5Ccline%7B1-1%7D%20%5C%5C%20%5Cleft%28%20%5Ccfrac%7Ba%7D%7B100%7D%20%5Cright%29%5Ccdot%20b%20%5C%5C%5C%5C%20%5Ccline%7B1-1%7D%20%5Cend%7Barray%7D~%5Chspace%7B5em%7D%5Cstackrel%7B%5Ctextit%7B75%5C%25%20of%20%22x%22%7D%7D%7B%5Cleft%28%20%5Ccfrac%7B75%7D%7B100%7D%20%5Cright%29x%5Cimplies%200.75x%7D%20%5C%5C%5C%5C%5B-0.35em%5D%20~%5Cdotfill%5C%5C%5C%5C%20%5Cstackrel%7B%5Ctextit%7B10%5C%25%20of%200.75x%7D%7D%7B%5Cleft%28%20%5Ccfrac%7B10%7D%7B100%7D%20%5Cright%290.75x%5Cimplies%200.075x%7D~%5Chfill%20%5Cstackrel%7B%5Ctextit%7Btotal%20percent%20savings%7D%7D%7B0.75x-0.075x%5Cimplies%200.675x%7D%20%5C%5C%5C%5C%5B-0.35em%5D%20~%5Cdotfill)

It is an expression, as an equation has an equal sign on it.
This has no equality property, therefore it is an expression.