Primary school sixth grade mathematics book 1 primary school homework page 92-93 answer
A school has 100 students taking part in the math contest, with an average score of 63, including 60 for boys and 70 for girls. How many more boys than girls?
Solution: For every X boys, there are (100-X) girls.
According to the meaning, {x * 60+(100-x) * 70}/100 = 63, the solution is X=70.