Susan had a bouquet of 3 dozen roses, which is 3*12=<<3*12=36>>36 flowers.
She gave half, 36/2=<<36/2=18>>18, to her daughter.
Then she placed her 36-18=<<36-18=18>>18 remaining flowers in a vase.
One-third of the 18 flowers in the vase wilted, resulting in 18/3=<<18/3=6>>6 wilted flowers.
After removing the wilted flowers, Susan had 18-6=<<18-6=12>>12 flowers remaining in the vase.
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