If 3 notebooks cost $3.51, how much would 7 notebooks cost?

Divide the 3.51 by 3 to get the price of one notebook.
Once you do this, you get a total of 1.17 for one notebook.
Now, just multiply 1.17 by 7 to get your total amount of money.
Once multiplied you get:
8.19

~Hope this helped :)

The first option would be correct if it were one half and not one