Given:
surveyed 3/4 of the population
2/3 of the surveyed students are into school clubs or sports team.
Multiply the fractions:
1) Multiply numerators
2) Multiply denominators
3) Simplify fraction
3/4 * 2/3 = 3*2 / 4*3 = 6/12
6/12 can be simplified into 1/2
4a) 3 rows and 4 columns
4b) 2 of the rows gray
4c) 4 of the gray squares black
4d) 1/2 of the students participate in school clubs or sports team