(208-64)÷2= 144÷2=72 points
The score of Xiaohua: 72+64= 138.
Suppose Xiaohua did the X question correctly.
20x- 12X( 10-x)= 138
32x- 120= 138
32x=258
X=8 questions
Assuming Xiaodong did the Y problem correctly,
20y- 12X( 10-y)=72
32y- 120=72
32y= 192
Y=6 questions