Mailboxes plus sends packages overnight for $5 plus $0.25 per ounce. United packages cost $2 plus $0.35 per ounce. Mr. Molinari noticed that his package would cost the same to maill using either service. How much does his package weigh?

First, set up 2 equations, one for each service, using w for weight. (I'm using x for the first service, and y for the second one)

x=5+0.25w

y=2+0.35w

Since the prices (x and y) end up being the same, we can set the equations equal to each other:

5+0.25w=2+0.35w

Now, we can simplify and solve for w, the weight.

3=0.1w

30=w

So, his package weighs 30 ounces.