nix/store error?

Repl link/Link to where the bug appears: https://replit.com/@Patricia-AnneA4/FluidUselessMacrolanguage?v=1

when I run a project for school:

```
# variables for all starting values
name = "Stacey"
num_apples = 12
num_pineapples = 2
num_bananas = 1
cost_apple = 0.6
cost_pineapple = 2.50
cost_banana_pound = 0.35
banana_pounds = 5
cash = 20
# calculate total items
total_items = num_apples + num_pineapples + num_bananas
# calculate total cost
total_cost_apples = num_apples * cost_apple
total_cost_pineapples = num_pineapples * cost_pineapple
total_cost_bananas = num_bananas * cost_banana_pound * banana_pounds
total_cost = total_cost_apples + total_cost_pineapples + total_cost_bananas
# calculate average price per item
avg_price = total_cost / total_items
# calculate change
change = cash - total_cost
# printing receipt
print("-----------")
print("Customer: " + name)
print("Number of Items: " + str(total_items))
print("Total Cost: $" + str(total_cost))
print("Average Cost: $" + str(avg_price) + " per item")
print("Paid: $" + str(cash))
print("Change: $" + str(20-13.95))
print("-----------")
```

i’ve done everything right but right before my code runs

my console says:

```
/nix/store/zqk3m21442kvpjwd3rh41wdavqkzkyik-python3-wrapper/bin/python3 $file
-----------
Customer: Stacey
Number of Items: 15
Total Cost: $13.95
Average Cost: $0.9299999999999999 per item
Paid: $20
Change: $6.050000000000001
-----------
```

as you can see there is a nix thing? and it messes up my change ??