Interpreting the problem.
The price includes GST.
∴ 18% GST means if the price without GST is ₹100 then price including GST will be ₹118.
Calculate the price before GST
When price including GST is ₹118, original price-₹100
When price including VAT is ₹1239,original price =100118×1,239
Thus, the price of the article before the addition of GST was ₹1050,