Someone came into my shop and stole $100 out of the register without my knowledge. the person came with the same $100 5 minutes later and he bought $70 in items and i gave him back $30 change. how much money did i

You lost $30 dollars out of the register and the other $70 dollars from the items. You basically lost $100. 

Lol it is 100! Omgee it's 100 ! What's wrong with yu ppl ! He stole 100$ After he stole the 100 it don't matter what he bought or came back with!

Let's say you have 200$ in your drawer to begin with, person stole 100$ so that puts your register to 100$ now. He came back bought 70$ worth of things and got 30$ back. Now the register is at 170. If he never stole the 100$ it would be at 270. So 270 what he suppose to have subtract the 170 he actually has=100 !!