It is easier if you evaluate the expression as a whole instead of finding the number in the numerator and then the number in the denominator.
When you're dividing, you subtract the power of 10 in the numerator by the power of 10 in the denominator, so for your example it is
7 - (-3) = 10
Then you have 36/12 = 3
And the answer is 3 * 10^10
I'm not familiar with math code like many helpers on this forum, so maybe someone else can write it more clearly if you can't understand what I mean.