Answer:
C. 560
Step-by-step explanation:
50% is one half, so there is another half of 280. 280*2=560
C
19.84
the decimal has to stay in the same place
0.000000084
we need to move the decimal 8 places to the right
8.4* 10^-8
Answer: what the heck do you have to answer
= 81