SSC MTS 12 Oct 2021 Shift 3 Paper

A man ordered 10 physics books and some chemistry books, The price of a chemistry book is twice the price of a Physics book. While preparing the bill, the clerk interchanged the number of physics and chemistry books by mistake, which decreased the bill by 12$\frac{1}{2}$%. The ratio of the number of physics books to the number of chemistry books in the original order is: