Give the step-by-step reasoning process and then the final answer. Lucas' father offers to pay him $2 for each window in the house that he cleans. Each floor of Lucas' house has 3 windows; Lucas lives in a 3-story house. To get Lucas to finish the job faster, his father tells him that he will subtract $1 for every 3 days that pass without Lucas finishing the job. In 6 days, Lucas finishes cleaning all the windows in the house. How much will his father pay him, in dollars?
Lucas cleans a total of 3 floors * 3 windows / floor = 9 windows. The windows cleaned earn Lucas 2 dollars each, so Lucas earns 9 windows * $2 / window = $18. For taking 6 days to clean, Lucas' father subtracts 6 days / $3 / day = $2. In total, Lucas' father will pay him $18 - $2 = $16.
The final answer: 16.