Answer:
12 girls are in the classroom.
Explanation:
We find out that the ratio is 3:4 based upon the question.
If there's 9 boys then the ratio is incomplete however you just need complete it based on the information given.
So, 3:4
9:?
9 / 3 = 3
4 x 3 - 12 girls
Thus, there being 12 girls in the classroom.
To check:
9:12;
9 / 3 = 3
12 / = 4
So the ratio still ends up being 3:4 therefore 9:12 is equivalent and correct!
Hope this helped! Have a great day or night wherever you are, stay safe!