When solving these proportions we just remember when moving a number from one side to the other if it started in the numerator it ends up in the denominator and vice versa.
I'll do it in two steps here for teaching purposes; it's not too hard to go directly to the answer.
[tex] \dfrac{13}{7} = \dfrac{10}{v} [/tex]
[tex]13 v = 7(10) [/tex]
[tex] v= \dfrac{7 \cdot 10 }{13} = \dfrac{70}{13} \approx 5.4[/tex]
