(2x+y)-((x+y)+3)=0

Solution for (2x+y)-((x+y)+3)=0 equation:

Simplifying
(2x + y) + -1((x + y) + 3) = 0

Remove parenthesis around (2x + y)
2x + y + -1((x + y) + 3) = 0

Remove parenthesis around (x + y)
2x + y + -1(x + y + 3) = 0

Reorder the terms:
2x + y + -1(3 + x + y) = 0
2x + y + (3 * -1 + x * -1 + y * -1) = 0
2x + y + (-3 + -1x + -1y) = 0

Reorder the terms:
-3 + 2x + -1x + y + -1y = 0

Combine like terms: 2x + -1x = 1x
-3 + 1x + y + -1y = 0

Combine like terms: y + -1y = 0
-3 + 1x + 0 = 0
-3 + 1x = 0

Solving
-3 + 1x = 0

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '3' to each side of the equation.
-3 + 3 + 1x = 0 + 3

Combine like terms: -3 + 3 = 0
0 + 1x = 0 + 3
1x = 0 + 3

Combine like terms: 0 + 3 = 3
1x = 3

Divide each side by '1'.
x = 3

Simplifying
x = 3