Answer:
36 boys
Explanation:
The question says that for every 7 girls there are 6 boys in the class. Using this line of reasoning we can say this:
For every 14 girls, there are 12 boys
For every 21 girls, there are 18 boys
For every 28 girls, there are 24 boys
For every 35 girls, there are 30 boys.
For every 42 girls, there are 36 boys.
You can see the pattern here, and there are 36 boys in that class.