(3.6x10^-5)/(1.8x10^2)

Answer 1

Multiply the numbers 3.6 x 1.8 = 6.48
Add the exponents from the base of 10
(-5 + 2) = -3
THus your answer is
6.48 x 10^-3
Always recall that your answer in scientific notation must be a number between 1 and 10 : )

Answer 2

I suggest you divide instead
(3.6x10^-5)/(1.8x10^2)
= (3.6/1.8) x 10^(-5-2)
= 2.0 x 10^-7