Elise is buying more dog food. She buys a 15kg bag then another 10kg bag, and she now has 40kg of dog food. How many kilograms of dog food did Elise already have?
Elise has bought a total of 15 kg + 10 kg = 
<gadget id="calculator">15+10</gadget>
<output>25</output>
25kg of dog food.
This means she already had 40 kg - 25 kg = 
<gadget id="calculator">40-25</gadget>
<output>15</output>
15kg of dog food.

<result>15</result>