Explanation:

- We start with a total of 60 students. The boys are $\frac{5}{7}$ times the number of girls.

- Let the number of girls be $x$. Then, the number of boys is $\frac{5}{7}\times x$. So, $x+\frac{5}{7}x=60$.

- Solving it gives $x=35$ (girls) and the boys are 25.

- The ratio of girls who like Rose to total girls is $2:7$, giving $\frac{2}{7}\times 35=10$ girls who like Rose.

- The number of boys liking Sunflower is 60% of girls liking Rose, so $0.6\times 10=6$ boys.

- Girls liking Sunflower are 2.5 times the boys liking Sunflower, thus $2.5\times 6=15$ girls.

- These girls are also 150% of the boys liking Lotus, which means $\frac{15}{1.5}=10$ boys like Lotus.

- Now we calculate:

- Boys liking Lotus and Sunflower: $10+6=16$

- Girls liking Sunflower and Rose: $15+10=25$

- The difference is $25-16=9$.

Your guess was 9, and indeed:

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