Answer
0.984
Work Step by Step
$\frac{18.7-6.6}{28.4-16.1}=\frac{12.1}{12.3}=0.98\underset\uparrow37398$
To round to 3 significant digits, count 3 digits from the left, starting with the first non-zero digit. The next digit to the right is 5 or greater, so add 1 to the final digit, then drop all other digits to the right.
