"All Items 20% Off Marked Price" is a sign at a local golf pro shop. Create a function and then use it to determine how much one has to pay for each of the following marked items: a $9.40 hat, a $13 umbrella, a $65 pair of golf shoes, a $12.60 golf glove, a $750 set of golf clubs.

80% times the price(x)

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To determine how much one has to pay for each of the marked items with a 20% off discount, you can create a function that takes the original price of an item as input and calculates the discounted price.

Here's an example of a function in Python that can be used for this purpose:

```python
def calculate_discounted_price(original_price):
discount_percent = 20 # 20% off discount
discount_amount = (discount_percent / 100) * original_price
discounted_price = original_price - discount_amount
return discounted_price
```

Now, you can use this function to calculate the discounted price for each item mentioned:

```python
hat_price = 9.40
discounted_hat_price = calculate_discounted_price(hat_price)
print("Discounted price for the hat: $", round(discounted_hat_price, 2))

umbrella_price = 13
discounted_umbrella_price = calculate_discounted_price(umbrella_price)
print("Discounted price for the umbrella: $", round(discounted_umbrella_price, 2))

golf_shoes_price = 65
discounted_golf_shoes_price = calculate_discounted_price(golf_shoes_price)
print("Discounted price for the golf shoes: $", round(discounted_golf_shoes_price, 2))

golf_glove_price = 12.60
discounted_golf_glove_price = calculate_discounted_price(golf_glove_price)
print("Discounted price for the golf glove: $", round(discounted_golf_glove_price, 2))

golf_clubs_price = 750
discounted_golf_clubs_price = calculate_discounted_price(golf_clubs_price)
print("Discounted price for the golf clubs: $", round(discounted_golf_clubs_price, 2))
```

Running this code will output the discounted price for each item based on the 20% off discount.

Note: In this example, the discounted prices are rounded to two decimal places using the `round()` function for better readability.