9(2k-3m)-9m-4(-3m-3k)

n = 20

Step-by-step Explanation:
When dealing with ratios, there is always most likely a second number given to you. This number is going to be 1.
When looking for n, you have to look for all of the numbers, in this case there is only two.
1 is the hour, so now you just need the 20 minutes.
If the ratio is 1:n, this means that n would have to equal 20.
1:20