This riddle I found

[Sirrus]

I have concluded that this is impossible.

[Ad Bot]

[dkamm65]

I'm starting to think it isn't possible.

[Big Brother]

Oh that was so obvious! Got the answer.

[chilmans]

o    o o
o o    o
o o o  
   o o o

You only took 4 away

Oh that was so obvious! Got the answer.

Tell us

[WhatevaGuy]

You only took 4 away

Dammit.  It was six, wasn't it.
:c

[Big Brother]

x o o x
o o x o
o o x o
x o o x

[chilmans]

That isn't right, amiright?

[Skip]

x o o x
o o x o
o o x o
x o o x

each row and column must have equal circles left.

[WhatevaGuy]

x o o x
o o x o
o o x o
x o o x

Nope.  Only two are in rows 1 and 4, whereas there are three in rows 2 and 3.

[chilmans]

I have concluded that this is impossible.

I think I'll agree

[Marcem]

o o o  
o       o
o       o
   o o o
What I got, but it doesn't work. :(

[Big Brother]

forget

[Peejster]

XOOX
OXOO
OOXO
XOOX?

[chilmans]

XOOX
OXOO
OOXO
XOOX?

nope

[Skip]

XOOX
OXOO
OOXO
XOOX?

each row and column must have equal circles left.