Math in the sixth grade: Xiao Wei did 20 Olympic math problems, with 8 points for one problem, no points for not doing it, 5 points for doing a wrong problem, and finally got 105. He answered several questions correctly. Assuming that the X channel is right, the Y channel is not, and the Z channel is wrong, then X, Y, Z, Y and Z are all integers greater than or equal to 0.

X+Y+Z=20 .............. equation 1

8X-5Z= 105 .............. Equation 2

Equation 1*5, plus Equation 2:

5X+8X+5Y+5Z-5Z=20*5+ 105

13X+5Y=205

Y=4 1- 13X/5

Therefore, x must be a multiple of 5.

And x must be greater than 10 (because the score of 105 is greater than 10*8=80) and less than 20 (because the score of 105 is less than 20*8= 160), so x can only be/kloc-.

y = 4 1- 13 * 3 = 2z = 20- 15-2 = 3。

Verification:

15*8-3*5= 105, so the answer is correct.

Do 15 right, do 3 wrong, don't do 2.