1) Gathering the data:
30 students
40% are girls then 60% are boys
2) Calculating
30 ----100%
x ------ 60%
x= 1800/100
x= 18 boys
[tex]\begin{gathered} \frac{30}{x}=\frac{100}{60} \\ 30\cdot60=100x \\ \frac{1800}{100}=\frac{100x}{100} \\ x=18\text{ boys} \end{gathered}[/tex]