A local bakery sells two types of pies: apple pies and cherry pies. The bakery has a total of 30 pies available today. If the number of apple pies is 10 more than the number of cherry pies, how many cherry pies are there?

Let

$ a = $ number of apple pies

$ c = $ number of cherry pies

The relationships can be summarized with the following equations:

$$ a + c = 30 $$

$$ a = c + 10 $$