First find the net amount of ivy Cary removes each day by subtracting the ivy's growth from the amount she removes: 6 feet/day - 2 feet/day = <<6-2=4>>4 feet/day
Then divide the total feet of ivy by the net amount Cary removes each day to find how many days it takes her to remove all the ivy: 40 feet / 4 feet/day = <<40/4=10>>10 days
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