Some interesting fill in puzzle

[boldsidewinder 0]

Fill in the circles with any number(no repeating) in a way that the sum of the numbers on a row or column are the same.

[rationaltiger]

@boldsidewinder-0 This is a fun problem!

I let a=leftmost ?, b=topmost ?, and c=bottomost ?

$$8+a=17+b=9+b+c=13+c$$
Then, $$17+b=9+b+c\Longrightarrow c=8,$$ so
$$13+c=17+b\Longrightarrow b=13+8-17=4$$ and $$8+a=13+c\Longrightarrow a=13+8-8=13.$$

That gives $$(a,b,c)=(13,4,8),$$ and those numbers work! (with the sum being 21).

[boldsidewinder 0]

@rationaltiger Correct!