What is the unknown number in this puzzle?

Question

I am going through some simple math problems in these quarantine days. Some of them are solved by me and some of them aren't solved by me. one of the unsolvable problems is given here:

Can you help me by giving any clue to fund the unknown number in the image?

Answer 1

Let the missing number be $x$ $$9=(10-7)^2$$ $$25=(15-10)^2$$ $$49=(15-8)^2$$ Therefore $$x={(8-7)^2}=1$$

Answer 2

It is $n=41$. This is the only number $0\le n\le 72$, where the combined number of $8,49,15,25,10,9,7,n$ is a prime number, namely $$ p=8491525109741. $$ Also, for $n=73$ the number is prime, but the largest number certainly sits at the base.