This can't be simplified much. The only like terms are the two terms with x^2.
6x^2 + y - x^2 + 5 + x - 3y^2
So, you can simplify to 5x^2 + y + 5 + x - 3y^2, but I don't see how you can simplify it any further.
6x^2 + y - x^2 + 5 + x - 3y^2.
To simplify the above:
There are 6 terms, separated by a + or - signs.
Group like terms along with their signs:
6x^2-x^2 + x + y-3y^2 + 5 (1)
Now 6x^2-x^2=5x^2. Replace accordingly.
5x^2+x -3y^2+y + 5. This is simlified form.
For the sake of order, but not necessary, the x's and y's are kept in a descending order and then constant term.