Answer:
A
Explanation:
A is the answer. Just the numerical coefficient is added. 6.4 +2.85 = 9.25
The 10^11 is a common factor to both numbers.
The question can be done as 6.4 * 10^11 + 2.85*10^11 = 10^11(6.4 + 2.85) = 10^11* (9.25). One further point: the answer should be 9.3*10^11.
6.4 has only 2 sig digits.
B is wrong. The powers do not add
C is wrong. The powers do not change under addition.
D is wrong. The addition did not exceed 10. I can't explain the thinking of making the power go up one.