To calculate this, we need to find how many students watch 6-7 hours of tv a week, and how many students watch 2-3 hours a week.
We have 10 students watching 6-7 hours a week, and 3 students watching 2-3 hours a week. The question is asking "How many more 6-7 than 2-3", which means to subtract 3 from 10.
I will now write out the equation as I rewrite the entire question.
How many more students watch 6-7 (10-) hours of tv a week than to how many watch 2-3 (3) hours a week? (=?)
Now, write out what we have in parenthesis.
10-3=?
Subtract 3 from 10.
10-3 = 7.
There are 7 more 6-7 hours of tv a week than there are 2-3 hours of tv a week.
I hope this helps!