If the comp sold for $199,000 but includes a $3000 porch and the subject has no porch, then we subtract the value of the porch to yield a base for the comparable of $196,000. Then, since the comparable has no pool or chimney, we add these values - $8,000 and $2,000, respectively - to that base value to yield an adjusted value of $196,000 + $8,000 + $2,000 = $206,000.