Find the original price if the price after reduction by $15\%$ and subsequent increase by $5\%$ is $1606.60$ euro I want to solve the following examples. Solution is 1800 euro. I used this formula: $S=\frac{100 i}{p}$, but I couldn't get the result. Please help me. The example is: The price of a product is reduced 15%, then the price is increased by 5%, and now the price is 1606.60 euro. Find the original price of the product. Thanks for your help.

Let $P$ the original price, $d=15\%$ the first reduction rate, $i=5\%$ the increaing rate and $S=1606.60$ the final price.

You have that $P$ is reducted to $P(1-d)=P'$ and then is increased to $P'(1+i)=S$; thus $$ S=P(1-d)(1+i)\Longrightarrow P=\frac{S}{(1-d)(1+i)}=\frac{1606.60}{(0.85)(1.05)}=1800 $$