output y(n): euler problem

ok this isnt really a homework question for me but rather i need a little help refreshing my memory as it has been awhile since i did this.

i need to find the output of a filter y(n)

with an input of X(n)= cos(n3∏/7)

and transfer function H(ω) = ((0.5-0.2e^(-jω))/(1+0.7e^(-jω)+0.1e^(-2jω))

the input and TF are in different domains, i know that i need to use euler's on the exp parts, but cant quite remember how to get to y(n).
any help will be apreciated