Answer:
Approximately 13.41
Step-by-step explanation:
First do square root of each, which is finding what number multiplies by its self to get the number.
For example: The square root of 80 is approximately 8.94, and the square root of 20 is approximately 4.47.
So: 8.94 + 4.47 = 13.41 (Add normally, but remember to put the decimal in the right place).
Hope this helped :)