To add two numbers in the UNIX/Linux awk command, you can use the + operator. For example, to add the numbers 5 and 10, you would use the following command:
awk 'BEGIN {print 5 + 10}'
This will print the result of the addition, 15, to the terminal.
Alternatively, you can use the awk command to read the numbers from a file or from standard input. For example, to add the numbers in the file numbers.txt, you could use the following command:
awk '{print $1 + $2}' numbers.txt
This will read the first two numbers in each line of the numbers.txt file, and print the sum of those numbers to the terminal.