Answer:
D) b = 
Step-by-step explanation:
First, move all the terms that do not include b to the left side with S:
S = 2ab + 2bc + 2ac
S - 2ac = 2ab + 2bc
Now, factor out 2b from the right side:
S - 2ac = 2b(a + c)
Divide both sides by 2(a + c):
b = 
Finally, multiply out the denominator:
b = 
X= -1.769292
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Rounding 2.199. The tenths digit is 1, which is 4 or less, so you will round down. Re-write 2.199 without the decimal places: 2 . So 2.199 rounds to 2.
Answer:

Step-by-step explanation:
In order to add or subtract numbers in scientific notation, the powers of ten must have the same exponent. In this caes the diameter of an average human body cell is a power of -4 and the diameter of a plant cell is a power of -3. In order to add them, we can move the decimal over for the body cell diameter:

Add the two values: 
Correct Choice is B.
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