Since you're figuring out what ratio is equivalent to 10/14, you need to divide 10/14 (top to bottom) by 2:
[tex] \frac{10}{14} [/tex] ⇒ [tex] \frac{10 divided by 2}{14 divided by 2} [/tex] ⇒ [tex] \frac{5}{7} [/tex]
So, [tex] \frac{5}{7} [/tex] or 5:7 is the ratio that is equivalent to [tex] \frac{10}{14} [/tex]