Danielle started with two dozen roses, or a total of 2*12=<<2*12=24>>24 roses.
Her trade added another dozen roses, for a total of 12+24=<<12+24=36>>36 roses.
The first night, half of the roses wilted, leaving 36/2=<<36/2=18>>18 roses.
On the second night, again half of the remaining roses wilted, leaving 18/2=<<18/2=9>>9 unwilted roses.
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