Rory makes a cake that weighs 20 ounces. She cuts into 8 pieces. Rory and her mom each have a piece. How much does the remaining cake weigh?
Each piece of Rory's cake weighs 20 ounces / 8 pieces = 
<gadget id="calculator">20/8</gadget>
<output>5/2 = around 2.5</output>
2.5 ounces.
If Rory and her mom each have a slice, they will have eaten 2.5 ounces + 2.5 ounces = 
<gadget id="calculator">2.5+2.5</gadget>
<output>5</output>
5 ounces.
The rest of the cake weighs 20 ounces - 5 ounces = 
<gadget id="calculator">20-5</gadget>
<output>15</output>
15 ounces.

<result>15</result>