213. Lilavati. Here is a small puzzle borrowed from "Lilavati" (1150 AD) by Bhaskara

"A beautiful maiden with beaming eyes told me a number. If this number is multiplied by 3, $\frac{3}{4}$ of the product is added, the sum is divided by 7, $\frac{1}{3}$ of the quotient is subtracted, the result is multiplied by itself, 52 is subtracted, the square root is extracted, 8 is added, and the sum is divided by 10, the result is $2$."

With the right approach, solving this puzzle, like many other ancient riddles, is incredibly easy.
213. The maiden named the number 28. The trick is to reverse the entire process of calculations: multiply 2 by 10, subtract 8, square the result, and so on. For example, remember that increasing a product by \(\frac{3}{4}\) means taking \(\frac{7}{4}\) of it. The reverse action involves taking \(\frac{4}{7}\).