Answer:
90
Explanation:
3 boys
5 girls,
Say that there where "x" number of groups like this, (x will be the total number of groups like this, if one were to divide the population by the number of groups, they would the number of students);
Set up an equation;
x ( 3 + 5 ) = 240
Combine like terms and distribute;
8x = 240
Inverse operations;
8x = 240
/8 /8
x = 30
Substitute back in to find the number of boys;
30 * 3 = 90