It looks like the next six terms are 22, 26, 30, 34, 38, 42
It is increasing by 4
The books are $5, and the magazines are $10. I’m not sure which way you want it explained but since magazines are twice the price of books, you can solve the equation 3b + 2b = 25. This gives you b=5 which you just multiply by 2 giving you the price of a magazine.
D.8
Multiply something to 6 that makes 48! So 6•8 would be 48!
7 over 8 can be seen as

or 7÷8.
This is what this question will look like on a calculator.

As you can see, you will only get 0.875 so your answer will be terminating.
Terminating = Answer Stops
ex.) 0.784 or 0.25
Repeating = Answer Repeats
ex.) 0.5555... or 1.33...
1 and 1/2 is the same as 1.5 and 1.5 * 4 is 6 so I would say 4