The problem above is related to the topic on <em>"Equivalent Ratios."</em> In order to find the missing term in a proportion, you can use cross products.
Let n be the<em> "missing term"</em> or<em> the number of miles that Bart Simpson can skateboard in 42 minutes.</em>
=
4 x 42 = 56n
168 = 56n
= n
3 = n
n = 3 miles
Therefore, it takes 3 miles for Bart Simpson to skateboard in 42 minutes.