This is a dual adder that has the transfer function
f(x, y, z) = -1 * (x + y + 10 * z)
and is implemented with two LF356N. Use the two trimmers to adjust the output voltage to 0V when no input voltages are applied.
This is the original circuit as described in Dr. Vogels Home Brew Analog Computer , except that a LF 356 is used instead of a LF 355.
The analog computer project files are hosted at GitHub: