Answer:
6
Step-by-step explanation:
lower quarter is 10
higher quarter is 16
16-10=6
There are 8 weeks and 18 books. therefore you would multiply these numbers together.
the answer would be 144 different combinations.
not sure about the permutation or combination notation, but I got you on the first part!
First you can solve for b: Subtract a on both sides and get 2b=-a+10, then divide by 2 to get b by itself and get: b=-1/2a+5
Then you can plug in this equation for b in the other: This would give you: 2a+-1/2a+5=6. Then you can use that equation to solve for a and get: 1.5a+5=6, subtract 5, 1.5a=1, divide by 1.5, a=1/1.5
Then you can plug in the value of a to solve for b.
Answer:
$8.8
Step-by-step explanation:

