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: 
Answer:
It's totally correct with no doubt
The answer would be (A) 14.47 gallons. Hope this helps!
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Answer:
Subtract 9 from both sides of the equation.