Answer: 0.00799
Step-by-step explanation:
The zeros in 0.00798516 are not considered significant because they are not between nonzero values.
If we had something like 1.207, then that zero would be considered significant.
The first three significant values we come across in 0.00798516 are 7, 9 and 8 in that order. The next digit 5 meets the criteria of "5 or larger", which means the 798 bumps up to 799. Erase everything to the right of that.
Therefore, 0.00798516 rounds to 0.00799 when rounding to 3 significant figures.