Answer:
x = -0.4
Step-by-step explanation:
We have the equation:
-9x + 0.4 = 4
First, the operation to move all the constants to the right side is subtraction since we would have to subtract 0.4 from each side, let's see this:

Now, we have all the constants on the right side of the equation.
Now, the operation we need to perform to isolate the variable is division (since the x has a -9 that is being multiplied by x) we need to do the opposite operation:

<h3>Thus, the answer to this equation is x= -0.4</h3>