In a class of 20 students, 40% are boys. twenty-five percent of the boys and 50% of the girls wear glasses. how many students wear glasses?

First, you need to figure out hoe many boys and girls there are.

40% = 0.4

0.4 x 20 = 8 boys

20 - 8 = 12 girls

25% of the boys have glasses

0.25 x 8 = 2 boys who wear glasses

50% of the girls have glasses

0.5 x 12 = 6 girls who wear glasses

2 + 6 = 8

8 students wear glasses

3x+9+4x+x=8x+9that's the answer for your question.