Answer and Explanation:
Since the question is asking for 'average tax rate' for Williams household, therefore, the tax rates are as follows:
$0 - $8,700 = 0.10
$8,700 - $35,350 = 0.15
$35,35 - $85,650 = 0.25
$85,650 - $178,650 = 0.28
$178,650 - $388,350 = 0.33
+ _____
1.11 = 1.11/5 = 0.222 or 22.2 % = Answer