Basic help with more than one variable

[Jewels]

I am trying to work with more than one variable and it wont let me. I am trying to expand (x+y)^8 but it keeps giving me an error. If I need to change the mode or something prior to allowing me to do this please let me know. I tried puting in expand ((x+y)^8,y,x). I have also tried to solve equations with mor than one variable. Is it the same problem?