let's say the original price was "x", and that'd be the 100%, the new price is 198 and that's 100% + 20% or namely 120%, so
[tex]\begin{array}{ccll} amount&\%\\ \cline{1-2} x&100\\ 198&120 \end{array}\implies \cfrac{x}{198}=\cfrac{100}{120}\implies \cfrac{x}{198}=\cfrac{5}{6} \\\\\\ 6x=990\implies x=\cfrac{990}{6}\implies x=165~\£[/tex]
