5×20= 100 (point) Assuming that all 20 channels are correct, you will get 100 point.

100-82= 18 (points) Assuming more than actual 18 points.

5+ 1=6 (points) If you replace a pair with a wrong question, you can subtract 6 points.

18÷6=3 (Dao) wrong question

20-3= 17 (Dao) Correct answer 17.