$69.69 - 51.54 + 73.64 = ? + 32.42$

$(2 \sqrt{392} - 21) + (\sqrt{8} - 7)^{2} = (?)^{2}$

$A$ number exceeds its two-fifths by $75$. The number is:

Natu and Buchku each have a certain number of oranges. Natu says to Buchku,"If you give me $10$ of your oranges,$I$ will have twice the number of oranges left with you." Buchku replies,"If you give me $10$ of your oranges,$I$ will have the same number of oranges as left with you." What is the number of oranges with Natu and Buchku respectively?

What is the Arithmetic mean of the first $n$ natural numbers?

Find a number,one-seventh of which exceeds its eleventh part by $100$.