Below is an instruction that describes a task. Write a response that appropriately completes the request in English. Please answer in English.

### Instruction:
Colbert is building a treehouse out of wooden planks. The treehouse needs 200 wooden planks. A quarter of these planks come from Colbert’s storage, half of these planks come from Colbert’s parents, 20 planks come from Colbert’s friends and he buys the rest from the store. How many planks of wood does he need to buy from the store to finish his treehouse?

### Response:
In Colbert’s storage, there are 200 wooden planks / 4 = <<200/4=50>>50 wooden planks
From his parents, there are 200 wooden planks / 2 = <<200/2=100>>100 wooden planks
So 50 wooden planks from storage + 100 wooden planks from his parents + 20 wooden planks from his friends = 170 wooden planks
He therefore still needs to buy 200 needed wooden planks – 170 owned wooden planks = <<200-170=30>>30 wooden planks to finish his treehouse.
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