I need some help with maths?

I am struggling to work out what to do. basically on fifa i got given 5k to trade with and then i give back the 5k including the profit i made with it. The first sale- i bought a player for 5k and sold at 6.2k. Then the next sale I bought a 10k player, meaning I put in 3.8k of my own coins. I sold it at 15k. What I want to know is how much I return to the guy, REMEMBER i put in 3.8k of my own coins. Please tell me, and also a word equation