If the owner sold the painting for a 10% increase in price, its retail price would be (1 + 0.1)*($3000) = 1.1*($3000) = $3300.
By the same logic, a 325% increase in price would be (1 + 3.25)*($3000) = 4.25*($3000) = $12,750 retail price. Remember that 100% is equal to 1.00 if written as a decimal, so 325% is written as 3.25. So, multiply 3000 (original price) by 3.25 to get the new retail price.