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

Then you have to find half of 36: 36/2 = <<36/2=18>>18 kg.

So, he sold 18 kg of vegetables.

# Answer

18
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
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?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
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user
18
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?
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