Thread: How to calculate the experimental error

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 ?

Pleasssss Help me