Final answer:
The 27.5 years straight-line method is used to depreciate residential real estate purchased after 1986.
Step-by-step explanation:
The method that can be used to depreciate residential real estate purchased after 1986 is the 27.5 years straight-line method. This method allows for equal deductions to be taken over a period of 27.5 years, with a straight-line depreciation calculation. In contrast, the 39 years straight-line method can be used to depreciate non-residential real estate purchased after 1986.