[tex]100\%-20\%=80\%\\\\\begin{array}{ccc}80\%&-&\£1200\\\\100\%&-&\£x\end{array}\\\\\\cross\ multiply\\\\80x=1200\times100\\\\80x=120,000\ \ \ \ |divide\ both\ sides\ by\ 80\\\\x=1500\ (\£)\\\\Answer:The\ computer's\ original\ price\ was\ \£1500.[/tex]
