i need some help with 7-8-9

7. Perform the operation and write your answer in scientific notation.

2.4 x 10^-9
——————
8x10^6


8. Perform the operation and write your answer in scientific notation.

(5x10^8) - (3.4x10^8)



9. Perform the operation and write your answer in scientific notation.
(3 x 10-8) + (2x× 10-6)