Rotating a vector 3 X degrees

Unity Engine
1

I am trying to rotate a vector 3 (2, 0, 0.5) X degrees, but can’t figure out the equation needed for that. Could someone please help? (No JavaScript, please =)

2 
Quaternion.Euler(0,90,0) * new Vector3(1,0,0)

This will roate the vector by 90° around the y axis.