If a newsboy receives a commission of .50centavos for every newspaper he sells, how much would his commission be if in a day he sold 30 newspapers?65 newspapers?100 newspapers?

I don't see what this has to do with a school party...

But if he get's .50 for every newspaper then you need to take .50 by how ever many newspapers he sells.

0.50(x) = Daily Commission

So plug the number of newspapers in for x and multiply.