Answer:
The question should say..... How much of the sample is left in......FIVE.....weeks? At least that is what I think you want to know.
The answer is 318.13 grams.
Step-by-step explanation:
450 - 6.7% = 419.85 grams ---- End of week 1
419.85 - 6.7% = 391.72 grams ---- End of week 2
391.72 - 6.7% = 365.47 grams ---- End of week 3
365.47 - 6.7% = 340.98 grams ---- End of week 4
340.98 - 6.7% = 318.13 grams ------ End of week 5