Elementary Algebra

$-13x+6y$
We start with the given expression: $-7x+9y+(-y)+x+(-2y)+(-7x)$ We use the commutative property to group like terms: $-7x+x-7x+9y-y-2y$ We use a form of the distributive property to combine like terms: $(-7+1-7)x+(9-1-2)y$ We add and subtract inside the sets of parentheses: $-13x+6y$