-12 I just did this question In class
Answer:

Step-by-step explanation:
The formula is 
<em>We need to solve for
, so we can perform the steps shown below:</em>

Hence, the third answer choice is correct.
Answer:
If two people have answered, you chose the one you want to give brainliest, and give them a crown on their answer.
Step-by-step explanation:
The ratio is basically finding the quotient of two numbers. If you want to find the ratio of horses to cows, divide the number of horses to that of cows.
Ratio = 18/27
When expressing it to its simplest form, make sure it is reduced. 18 and 27 are both factors of 9. So,
Ratio = 9*2/9*3
Cancelling out 9, the ratio at its simplest form is: <em>2/3</em>