Answer : 2,881.2 vacuum cleaners will be sold three months from now.
Steps: 8400*0.7=5880 -> 1 month from now (It’s 0.7 because it decreases by 30% so 70% will remain) 5880*0.7= 4116 -> 2 months from now 4116*0.7= 2881.2 -> 3 months from now
*note that this solution is based on the assumption that the 30% refers to it decreases by 30% of the previous months amount of vacuum cleaners sold, and not the amount of vacuum cleaners sold this month. If it were based on the amount of vacuum cleaners sold this month, the answer would be 840. (8400*0.1)
