ANSWER
30 students
EXPLANATION
There are 12 male students in the class.
That represents 40% of the class.
Let the total population of the class be x.
So, that means that:
[tex]\frac{40}{100}\cdot\text{ x = 12}[/tex]Now, we solve for x:
[tex]\begin{gathered} 40\cdot\text{ x = 12 }\cdot\text{ 100} \\ \Rightarrow\text{ x = }\frac{12\cdot\text{ 100}}{40} \\ x\text{ = }\frac{1200}{40} \\ x\text{ = 30 students} \end{gathered}[/tex]There are 30 students in the class.