How to ask my uncle for money?

My friend is selling her iphone to me its a 3gs 32gb for 180$. But some other guy wants to buy it from her for $275 and this guy has really been nagging her to sell it to him. Since we're friends she's selling it to me if I come with the cash on time. My uncle seems to be cool. He usually says to me "if i need anything just ask him for it and if I have it I will give it to you". I just want to buy it before that other dude buys it. I only need like $100

Maybe your uncle doesn't have the money at this time. Be a real friend and let your friend make a nice chunck of change with the other guy.

Ok first ask your parents if its ok to check with your uncle, then have a plan, with dates and where the money is coming from to pay him back, if you don't have any reliable source to pay him back, forget it