Let's first simplify the left side of the equation:

(x+a) + (x+2a) - (x-3a)
x + a + x + 2a - x + 3a
x + x - x + a + 2a + 3a
2x + 6a

Now simplify the right side of the equation:

(х-a-b) + (2x+3a+b) = (2a-b) - (2a-5b)
x - a - b + 2x + 3a + b = 2a - b - 2a + 5b
3x + 3a = 3b

So, the equation becomes:

2x + 6a = 3b

Therefore, the simplified equations are:
2x + 6a = 3b
3x + 3a = 3b