Answer: The person with the least score is at least 1, 2, 3, 4 points less than the other four people, so the person with the least score should be [423-( 1+2+3+4)]↓5 = 82.6 points, and the person with the least score will get 82 points at most.
Boys are divided into male 1 and male 2, while girls are divided into female 1, female 2, female 3 and female 4.
The meaning of the question is: female 1- male 2=4.
Male 1- female 4=4
And because the number of questions they answered correctly is different, at most 10 questions and at least 4 questions.
So there are only four possibilities: 10, 9, 8, 7, 6, 5, and the least possible is a girl or a boy.
If there are at least girls, the girls' score is 4=4, so the boys' score is 1 = 8, the girls' score is 1 = 10, and the boys' score is 2=6, so the other girls' scores are 9, 7 and 5. This situation holds!
If it is at least a boy, then the female is 1=8, the male is 1= 10, and the female is 4=6. There is only 7 between female 1 and female 4, but there are two girls, so this situation is not true!
To sum up, boys can do up to 8 questions ~ ~