Mary needs school supplies. She has 6 classes and needs 1 folder for each class. She also needs 3 pencils for each class. She decides that for every 6 pencils she should have 1 eraser. She also needs a set of paints for an art class.  Folders cost $6, pencils cost $2, and erasers cost $1. If she spends $80, how much did the set of paints cost in dollars?
Mary needs 6*1= 
<gadget id="calculator">6*1</gadget>
<output>6</output>
6 folders.
Mary needs 6*3= 
<gadget id="calculator">6*3</gadget>
<output>18</output>
18 pencils.
Mary needs 18/6= 
<gadget id="calculator">18/6</gadget>
<output>3</output>
3 erasers.
Mary spends 6*6= $
<gadget id="calculator">6*6</gadget>
<output>36</output>
36 on folders.
Mary spends 18*2= $
<gadget id="calculator">18*2</gadget>
<output>36</output>
36 on pencils.
Mary spends 3*1= $
<gadget id="calculator">3*1</gadget>
<output>3</output>
3 on erasers.
Mary spends 36+36+3= $
<gadget id="calculator">36+36+3</gadget>
<output>75</output>
75 on all the supplies except the paints.
Mary spends 80-75= $
<gadget id="calculator">80-75</gadget>
<output>5</output>
5 on the paint set.

<result>5</result>