Answer: 10 kg of the yam not sold
Step-by-step explanation:
We will find out how many kg of the yam was not sold.
If he sold exactly 2/3 of the yam, then 3/3 - 2/3 = 1/3 of the yam is left. In mathematics, "of" means multiplication.
30 kg * 1/3 = 10 kg of the yam not sold
