Harper has 15 rubber bands. His brother has 6 fewer rubber bands than he has. How many rubber bands do they have together?
His brother has 15 rubber bands - 6 rubber bands = 
<gadget id="calculator">15-6</gadget>
<output>9</output>
9 rubber bands.
They have 15 rubber bands + 9 rubber bands = 
<gadget id="calculator">15+9</gadget>
<output>24</output>
24 rubber bands together.

<result>24</result>