Riddle please solve for Brainly !!!!

You toke 250 from 2 friends
(Adds up to $500)
You buy a item for $450
($50 left)
Your friend asks for $30 bucks (you have $20 left)
You give them back $10 to each friend
They now need $240 EACH
you give them the amount
Then the friend that borrowed $30 gave it back you give it back which adds up to $510
WHERE DID THE EXTRA $10 COME FROM?