Answer:
5
Step-by-step explanation:
In all right triangles, the tangent of an angle is equal to its opposite side divided by its adjacent side (neither of sides may be the hypotenuse). Thus, we have:
[tex]\tan 60^{\circ}=\frac{5\sqrt{3}}{y},\\y=\frac{5\sqrt{3}}{\tan 60^{\circ}}=\boxed{5}[/tex]
