Answer:

Explanation:
In this question, we're trying to find how many boys and girls are in the class.
Lets get some important information that will help us to answer the question:
Important information:
- 21 students in Mrs. Clark's class
- 3/7 of the class are boys
- 4/7 of the class are girls
With the information above, we can solve the question.
To make this easier, we could turn the fractions into percents.

Now, we could just multiply 21 by the right decimal in order to get the right amount of boys and girls in Mrs. Clark's classroom.

When you solve, you would figure out that there are 9 boys and 12 girls in Mrs. Clark's class.
I hope this helped you out.
Good luck on your academics.
Have a fantastic day!