First, add the 4 plants Mark gave away to the 20 he has left: 4 + 20 = <<4+20=24>>24

Then divide this number by 2 to find how many plants Mark had after two months: 24 / 2 = <<24/2=12>>12

Then divide that number by 2 to find how many plants Mark had after one month: 12 / 2 = <<6=6>>6

Finally, divide that number by 2 to find out how many plants Mark initially planted: 6 / 2 = <<6/2=3>>3

# Answer

3
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Mark plants some strawberries in his backyard. Every month, the number of strawberry plants doubles. After 3 months, Mark digs up 4 strawberry plants and gives them to his friend.  If he still has 20 strawberry plants, how many did he initially plant?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
3
Mark plants some strawberries in his backyard. Every month, the number of strawberry plants doubles. After 3 months, Mark digs up 4 strawberry plants and gives them to his friend.  If he still has 20 strawberry plants, how many did he initially plant?
train