Answer:
A=11/12
Step-by-step explanation:
1/3+a=5/4
1/3+a-1/3=5/4-1/3
1/3+a-1/3
5/4-1/3 11/12
To determine the total class the whole class spent, you just have to simply add the individual costs of the three books. Using parenthesis, the solution can be written in the following two ways:
($15 + $9) + $12 = $36
$15 + ($9 + $12) = $36
No matter where you put the parenthesis, the final answer doesn't change. This is because of the Commutative Property of Addition. The order does not matter.
Answer:

Step-by-step explanation:
The original board is 40 1/8 inch and it is cut in 3 pieces of equal length:
New boards = 
And now he cuts again 3 3/4 inches off of each one of the new boards (substracts)

I think the answer is yes