Rachel drinks 2 glasses of water on Sunday and 4 glasses of water on Monday. Then she drinks 3 glasses of water every day for the next 4 days. One glass of water is 10 ounces of water. If Rachel wants to drink a total of 220 ounces of water in the week (Sunday to Saturday), how many glasses of water should she drink on Saturday?
From Sunday and Monday, Rachel drinks 2 + 4 = 
<gadget id="calculator">2+4</gadget>
<output>6</output>
6 glasses of water.
From Tuesday to Friday, Rachel drinks 3 * 4 = 
<gadget id="calculator">3*4</gadget>
<output>12</output>
12 glasses of water.
The total glasses of water she drinks from Sunday to Friday is 6 + 12 = 
<gadget id="calculator">6+12</gadget>
<output>18</output>
18 glasses of water.
The total ounces of water she drinks from Sunday to Friday is 18 * 10 = 
<gadget id="calculator">18*10</gadget>
<output>180</output>
180 ounces.
The ounces of water she should drink on Saturday is 220 - 180 = 
<gadget id="calculator">220-180</gadget>
<output>40</output>
40 ounces.
The glasses of water she should drink on Saturday is 40 / 10 = 
<gadget id="calculator">40/10</gadget>
<output>4</output>
4 glasses of water.

<result>4</result>