wifi slow, but wired internet fast?

okay so i just got a new laptop a week ago the Lenovo ideapad y400 and one thing i notice is that my wifi on the laptop is extremely slow i would run 5-10 mbps. While on wired connection i run 20-30 mmnbps. here the wierd thing o n my dads laptop he gets 20-30 mbps.idk whats is the problem. is it my laptop or my router??? PS at my brothers house his wifi is fast i run 30mbps max