Of 50 farmers, 25 grow cashew nut, 16 grow both cashew and maize, and 10 grow neither. How many grow maize only?

1. Since 10 grow neither, the union is $n(C\cup M)=50-10=40$. 2. Use $n(C\cup M)=n(C)+n(M)-n(C\cap M)$. 3. Substitute: $40=25+n(M)-16$, so $n(M)=31$. 4. That 31 is everyone growing maize, including the 16 who also grow cashew. 5. Maize only is therefore $31-16=15$. Answering 31 stops one step early and counts the overlap twice over. _Source: NECTA CSEE 2022 Basic Mathematics 041, Question 3: Sets and Probability_