Question

How? I don't fully understand this

Answer 1

`(9\cdot 10^9)\cdot (-2\cdot 10^(-3))\implies (9)(-2)\qquad (10^9\cdot 10^(-3)) \\\\\\ (-18)\qquad (10^(9-3))\implies -18\cdot 10^6`

Answer 2

Answer: A

Explanation:

(9*10^9)*(-2*10^-3)=

9*(-2)*10^9*10*-3=

-18*10^(9+(-3))=

-18*10^(9-3)=-18*10^6 ==> A