Add them first. 34.719 + 51.626 = 86.345.
You can find where the hundredth place is. It's always two places from the decimal. So in 86.345, the hundredth is 4.
The answer is A. 86.35. It's because the number that is beside 4 is 5. If the number is 4 and below, you don't round. If the number is 5 and above, you round it.