A coefficient is the number directly in front of the letters. For example,
the coefficient of 8p is 8. They isolated the coefficient to just one term.
A Term is a small group of whole equation. for example, the terms in this problem would be 6pq, 8p, and -6r.
A constant is a number by itself, so with no number behind it.
A variable is the letter. So in 8p, p is the variable.
All of this is just to give you a deeper understanding for when the problems will require more from you.
If you haven't guessed by now, the final answer is 6.