Mr. Alonzo was able to sell 125.5 + 78 = <<125.5+78=203.5>>203.5 kg of tomatoes.

So, there are 245.5 - 203.5 = <<245.5-203.5=42>>42 kg unsold tomatoes.

# Answer

42
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Mr. Alonzo harvested 245.5 kg of tomatoes. He sold 125.5 kg to Mrs. Maxwell and 78 kg to Mr. Wilson. How many kilograms of tomatoes are not sold?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
42
Mr. Alonzo harvested 245.5 kg of tomatoes. He sold 125.5 kg to Mrs. Maxwell and 78 kg to Mr. Wilson. How many kilograms of tomatoes are not sold?
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