6 dozen were purchased
divide the charge by the cost of one dozen
number purchased = 
= 6
.60 * 42 = 25.2
So, he/she would have answered 25 questions correctly.
N is a variable in algebra. Variables are letters that represent unknown numbers. Variables can be any letter of the alphabet.
Here's how to use n in an algebraic equation:
5 + n = 12
To find what N represents, let it be the only thing on the left side of the variable:
5 -5 + n = 12 - 5
n = 7
Happy to help!
The third one is r=-10 (don't forget the negative!)
The fourth one is p=-3 (again, watch for the negative)
((I can't get the fifth one, sorry. You might want to repost another question with just that one))
The sixth one is w=35.
Hope this helped a little bit! Sorry I couldn't help with all of them .-. Good luck though!
