^^ yes
1, you eliminate the y's from the equations
substituting the second equation into the first.
so x(x^2 - 5x + 6) = 5
2.)
3^2004 = 9^1002 = 81^501
and you can see the last digit is 1 in the expansion, so the remainder is 1.
(81*81 = xxx1 then you multiply by 81 again, but...