First of all, the minus sign before the parenthesis changes the sign of all the terms inside:
[tex] 3y-(y+2x)+x = 3y-y-2x+x [/tex]
Now, we can sum like terms:
[tex] 3y-y = 2y,\quad -2x+x = -x [/tex]
So, the final expression is
[tex] 2y-x [/tex]
