In a classroom which has 20 students,16 of the students are boys,24 are ten year old and 6 are girls who are not ten years old. How many students in the class are ten-year old boys?
A 8 B 10 C 12 D 15 E 16
We can't have 24 10-year-olds in a class of 20,
nor can we have 6 girls if 16 are boys.
Can you double-check the question ?
Presumably there are 30 students in the class.
Then, if you arrange the situation as sets,
with x being the number of 10-year-old boys
30=16-x+x+24-x+6
30=46-x
Hence, all the boys would be 10 years old