Mr. Alonzo was able to sell 125.5 + 78 = 203.5 kg of tomatoes. So, there are 245.5 - 203.5 = 42 kg unsold tomatoes.
This justifies what answer for what question? Q & A:
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?
42