Billy spent $30 on a t-shirt a sandwich and two books the t-shirt cost $8.95 in the sandwich cost $7.25 the books each cost the same amount how much did each book cost

To find out how much each book cost first we will subract to find out how many 2 books cost. Then we will divide. last but not least we will check our wok. Lets do it:- 

30 - 8.95 = 21.05
21.05 - 7.25 = 13.80

CHECK OUR WORK:-

13.80 + 7.25 = 21.05
21.05 + 8.95 = 30
We were RIGHT!!!

Now lets divide:-

13.80 ÷ 2 = 6.90
1 book costs $6.90.

CHECK OUR WORK:-

6.90 × 2 = 13.80
We were RIGHT

So, 1 book costs $6.90.

Hope i helped ya!! 

Yes, two vertical lines can be complementary

The answer is the first one