<human>:  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?
<bot>: How many kg of vegetables did the merchant install? ** You first need to know the total weight of the vegetables, so you add each quantity: 15 + 13 + 8 = <<15+13+8=36>>36 kg
How many kg of vegetables did the merchant sell? ** Then you have to find half of 36: 36/2 = <<36/2=18>>18 kg.
What mass of vegetables did he sell? ** So, he sold 18 kg of vegetables.
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