Answer:
45 and 47
Step-by-step explanation:
Are you serious?
The correct answers are B. , D. and E.
Good luck!!!!
Answer:
???69
Step-by-step explanation:
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: 
So, the negative would be divided out to make it 3, then square both sides to get rid of the square root and get 9, then subtract 15 and you get -6. <span />