Q:

why am I getting unused argument using c in r? 

When I try:
x=c(1,2,3)
...I get the message unused argument (3)
When I type x=c(1,2) it takes the function but when I type x it gives me a value of [3].  I want to create a simple vector of numbers but I don't know why it is giving me this message. 

A:

I presume you created a user-defined function called c, thereby replacing the built-in base-r function.  Try rm("c") and then everything should work as expected again.