A sandwich store charges a delivery fee to bring lunch to an office.
Delivery cost - D
Meatball sandwich cost - M
One office pays $40.50 for 5 meatball sandwiches.
40.50 = 5M + D
Another office pays $66.50 for 9 meat ball sandwiches
66.50 = 9M + D
A. How much does each meatball sandwich add to the cost of delivery?
D = 40.50 - 5M = 66.50 - 9M
40.50 - 5M = 66.50 - 9M
9M - 5M = 66.50 - 40.50
4M = 26.00
M = 6.50
B. What is the delivery fee
D = 40.50 - 5M = 40.50 - 5(6.50) = 40.50 - 32.50 = 8.00
Check
66.50 = 9M + D = 9(6.50) + 8 = 58.50 + 8.00 = 66.50
The answer to 8a. is 17, the answer to 8b. is 3.9, the answer to 8c. is 1 / 2, the answer to 8d. is 7 7 / 8, the answer to 9a. is commutative property, the answer to 9b. is multiplicative identity property, the answer to 9c. is associative property, and the answer to 9d. is additive inverse property.
Regarding the whole "explain using mental math" thing, I pretty much just used the fact that 8a. and 8b. both had the same number of decimal places. For 8c., I just made each number have a denominator of 10. And last, for 8d., all of the denominators were already the same, which made it pretty easy. I apologize for this section of my answer being so informal lol, I haven't had to do these kinds of problems in like 5 years <span />
Answer:
The object travels 144,000,000 feet.
Step-by-step explanation:
The distance the object travel after t seconds is given by:

How far would the object travel after 1.5 * 10^3 seconds
This is d when
, so 

The object travels 144,000,000 feet.
Answer:
Step-by-step explanation:
Perimeter is all sides added together.
l is length, w is width, and P is perimeter.

Answer: It is a difference of two squares, and it factors to (3x-7)(3x+7)
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Explanation:
We can write the 9x^2 as (3x)^2 since
(3x)^2 = (3x)*(3x) = (3*3)*(x*x) = 9x^2
The 49 can be written as 7^2 because 7^2 = 7*7 = 49.
This means 9x^2 - 49 is the same as (3x)^2 - 7^2. We have a difference of two squares.
The difference of squares factoring rule is
a^2 - b^2 = (a-b)(a+b)
which we have a = 3x and b = 7 in this case
So,
a^2 - b^2 = (a-b)(a+b)
(3x)^2 - 7^2 = (3x-7)(3x+7)
9x^2 - 49 = (3x-7)(3x+7)
Side note: This is the same as (3x+7)(3x-7). We can multiply two numbers in any order.