Answer:
[tex]\frac{2}{3}\\[/tex]
Step-by-step explanation:
If you have the numbers [tex]a[/tex] and [tex]b[/tex], the ratio of number [tex]a[/tex] to number [tex]b[/tex] is [tex]a:b[/tex] or [tex]\frac{a}{b}\\[/tex].
If [tex]\frac{2}{5}\\[/tex] of the students who study a language studies French, then the rest of them, [tex]\frac{3}{5}\\[/tex], doesn't study French. The ratio of the students who study French to the students who don't study French should be [tex]\frac{2}{5} : \frac{3}{5}\\[/tex].
[tex]\frac{2}{5} : \frac{3}{5} \\ \frac{\frac{2}{5}}{\frac{3}{5}} \\ \frac{2}{5} \cdot \frac{5}{3} \\ \frac{10}{15} \\ \frac{2}{3}[/tex]
