Answer:
B
Step-by-step explanation:
Let say, a=9,b=11,c=6
Then associative properties says that every element is related to each other, here "b" associates a &c.
Therefore, a is related to b+c
c is related to a+b
Answer:
40/9
Step-by-step explanation:
Use the work formula,
+
=
, where A is the amount of time it takes one person, B is the amount of time it takes another person, and T is the time it takes for them to work together.
Plug in the times for David and Alex alone:
+
= 
Find the least common denominator, which is 40.
+
= 
= 
Cross multiply and solve for T:
9T = 40
T = 40/9
So, if they worked together, it would take them 40/9 hours
Answer: 5 bags of sand
Step-by-step explanation:
Given
There are 8 elementary schools
3 Tons of sand is needed
It is contained in a 50- Pound bag
1 ton is equivalent to 2000 Pound
No of 50- Pound bag required is

These 40 bags will be required in 8 schools. So, each school requires

Answer:
Surface Area= 144
Step-by-step explanation:
To find the area of the triangle you would multiply the base times the height and divide it by 2. 9x6/2=27. For one triangle the area is 27. Since there are 4 you would multiply it by 4. 27x4= 108. This will give you 108. Now all you need to do is add the square which is 6x6= 36. 108+36=144.