Answer: 493.41
Explanation: We have been asked to subtract 15.54 from 508.9538.
Thus 508.9538 - 15.54 = 493.4138
By using the rules for significant figures for subtraction, round the answer to the least number of places to the decimal point of any number in the problem. As one number contains 2 decimal places and the other number contains 4 decimal places.
Thus the answer should have 2 decimal places. Thus the answer should be 493.41.