Op-amp homework question using potentiometer with my attempt at solving it
The trick with circuits involving a potentiometer is to replace the pot-meter by a resistor network whose values depend on the wiper position:

So you see than when \$k=0\$, the wiper is on the upper position 1 and the low-side resistance is the pot-meter value. On the opposite, when \$k=1\$, the wiper is in the lower position 2 and the low-side resistance is 0 ohm while the upper one is now the pot-meter value. Following this method and considering the superposition theorem, you should be able to adapt it to a 20-turn potentiometer and answer the question.