CTRL-----2.2kΩ----PS------GND

In terms of circuit between CTRL and GND, I think I get something like this:

By inspection and performing a nodal analysis, where i1 is the current flowing through R1, i2, the current flowing through R2 + R3 and i3, the current flowing through R4, and finally vx the voltage at the node where the 3 currents meet, I get:

i2 = i1 + i3

⇔ (vx/(R2 + R3)) = (V2 - vx)/R1 + (V1 - vx)/R4

using the calculator I get the correct result for vx, but when I tried to solve the equation prior to replacing the letters by their respective values, I can't get to the same result.

My work is this:

But I think is gone wrong somewhere!

Can anyone help me find where?