Let's simplify the equation step by step:

20 - (x*20 + 120) = 400 + 20

First, distribute the negative sign inside the parentheses:

20 - 20x - 120 = 420

Combine like terms on the left side:

-100 - 20x = 420

Now, isolate the variable x by adding 100 to both sides:

-20x = 520

Finally, divide by -20 to solve for x:

x = -26

So, the solution to the equation is x = -26.