So we are given a weight in grams and we need to find the area in(I'm assuming) square miles. Before we can solve this problem we need to come up with a few relationships.

We know: "8 1/2-inch-by-11-inch sheet of cardstock weighs 10 grams"

So:

Also we know: "1 inch= 30 miles"

So, by squaring both sides we get:

Also we know we have: 5grams(of cardstock)

Now we have everything we need to solve this problem, it's as simple as multiplying the relationships and canceling out units.

You'll see that everything cancels out and you are left with an answer in