solved arthmetic and string lab tasks

StringLab.py

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+sentence = "Artificial Intelligence is an evolution that help human achieve their goals"
+word = "evolution"
+print (f"the lenght of sentence is:{len(sentence)}")
+print(f"first occurrence index", sentence.find(word))
+print(f"word counts:{sentence.count(word)}")
+print(f"Uppercase:{sentence.upper()}")
+print(f"Lowercase:{sentence.lower()}")
+new_sentence = sentence.replace(word,"Progress")
+print(f"new sentence:{new_sentence}")
+print(f"last charecter: {sentence[-1]}")
+

main.py

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+price = 3
+quantity = 4
+tax_rate = 0.020
+subtotal = price*quantity
+tax = subtotal*tax_rate
+total = subtotal + tax
+print(f"Price of item:${price:.2f}")
+print(f"quantity:{quantity}")
+print(f"Tax rate:{tax_rate*100}%")
+print()
+print (f"Subtotal: ${subtotal:.2f}")
+print (f"Tax: ${tax:.2f}")
+print (f"Total: ${total:.2f}")