Aspirin (2-acetoxybenzoic acid) has the structure $\mathrm{CC}(=\mathrm{O})\mathrm{Oc}{}_1\mathrm{ccccc}{}_1\mathrm{C}(=\mathrm{O})\mathrm{O}$ (SMILES). How many of its carbon atoms are $s{p}^2$ hybridised?

Aspirin has 9 carbon atoms. The six aromatic carbons are $s{p}^2$ and the two carbonyl carbons (ester and acid) are $s{p}^2$, giving 8. Only the methyl carbon is $s{p}^3$.