This is super easy!

Let's just do one:

We just multiply straight across...

Now, think about it...

is like ...

Cut a pizza into 10 pieces

and look at 9 of the pieces:

We want of these

That would be 3 pieces. Right?

That's !

Just what we got by doing the math! Cooooool.

Now that we get what's going on, we can just go for it.

Here's another one: