Question

Which of the following is the same as 8.4 × 10 to the second power?

Answer 1

I believe the answer would be C.) 840

Answer 2

1) $8.4 \times 10^{2}$  is the same as $8.4 \times 100$ because the order of operations state to perform the exponents before multiplication. 
$8.4 \times 100 = 840$

The answer is C) 840

2) I'm assuming the second thing you said was a typo, but 8.4 × 10*2 is the same as 8.4 x 20, for the same reason above. 8.4 x 20 = 168.