How to calculate the error

I have two numbers:

The first number is 68.7 and this number is the average of 8 samples, the standard error of the mean is 5.9

The second number is 27 and this number is the average of 12 samples, the standard error of the mean is 1.4

I have to find the percentage of the second number by using:

27 divided by the (68.7+27).

How can I find the percentage of the error ?