A fruit and vegetable merchant installed 15 kg of carrots, 13 kg of zucchini and 8 kg of broccoli. He sold only half of them. What mass of vegetables did he sell?
You first need to know the total weight of the vegetables, so you add each quantity: 15 + 13 + 8 = 
<gadget id="calculator">15+13+8</gadget>
<output>36</output>
36 kg.
Then you have to find half of 36: 36/2 = 
<gadget id="calculator">36/2</gadget>
<output>18</output>
18 kg.
So, he sold 18 kg of vegetables.

<result>18</result>