Do you mean subtract two each day? If so...
4x3=12 and 12 divided by 2 is 6 so it would take six days to reach zero
or
you could manually subtract two from 6 each days as in 12-2=10 (1 day), 10-2=8 (2 days), and so on...
The area is equal to 230 CM.
area for rectangle :
area = width times length
area = 7 x 20 = 140CM
area for triangle:
area = 1/2 times base times height
area = 1/2 x 20 x 9 = 90CM
ADD:
140+90 = 230 CM
If u subtract 6-9 u would get a -3 because the 9 is bigger than the 6 so thats how you get a -3.