i am new to unity...i want to implement game somewhat like Brain Tuner ..

.in that game randomly numbers are appearing…the numbers are inserted into GUI text or GUI texture…?plz help…how to add GUI for inserting numbers or for operators(+/-) like brain tuner…

That sounds pretty basic, sounds like you need to learn a thing or two about programming. There are some helpful learning links in my signature for you.

Quick tip, you can use int randomNumber = Random.Range(min, max) to make a random number.