Rick held a fundraiser and is figuring out who still owes money. He marked on a sheet how much everyone has promised to contribute, but he forgot to note how much some people had actually paid. Altogether, everyone has promised to contribute $400, and Rick has actually received $285.  Sally, Amy, Derek, and Carl all still owe money. Sally and Carl both owe equal amounts, Amy owes $30, and Derek owes half as much as Amy. How much, in dollars, do Sally and Carl each owe?
In total, Rick is still owed 400 - 285 = $
<gadget id="calculator">400-285</gadget>
<output>115</output>
115.
Derek owes half as much as Amy, so he owes $30 / 2 = $
<gadget id="calculator">30/2</gadget>
<output>15</output>
15.
This means that Sally and Carl owe a combined total of $115 - $30 - $15 = $
<gadget id="calculator">115-30-15</gadget>
<output>70</output>
70.
As they owe equal amounts, they therefore owe $70 / 2 = $
<gadget id="calculator">70/2</gadget>
<output>35</output>
35 each.

<result>35</result>