Question

8/x=2/5

Answer 1

You could do that cross multiplication if you prefer.

Answer 2

Or you could flip both sides.

Answer 3

\[\frac{a}{b}=\frac{c}{d} => ad=cb \]
\[\frac{a}{b}=\frac{c}{d} => \frac{b}{a}=\frac{d}{c} \]
and i'm assuming none of these values are zero