Solve with the correct number of sig figs...
For addition and subtraction use the following rules: Count the number of significant figures in the decimal portion ONLY of each number in the problem. ... Your final answer may have no more significant figures to the right of the decimal than the LEAST number of significant figures in any number in the problem.
Here the least no of terms in right of the decimal is in 16.5 so the final answer should have only one significant value after decimal.
But we will only write one significant value after decimal so the final answer is