Respuesta :
Answer:
129
Step-by-step explanation:
Each day, Monica measures the amount of change in the number of bacteria and this number from each day gives a geometric series
3, -6, 12, -24, ...... having first term 3 and the common ratio -2.
Then the sum of the amount of change in the bacteria after the seventh day will be ( 3 - 6 + 12 - 24 + 48 - 96 + 192) = 129 (Answer)