#2: zeros
Ex: 23.000000(zeros at the end of a decimal don’t change its value it’s still 23)
#4: difference
If you are subtracting(.31 + 0.108) - (0.1 + 0.3) then you are calculating or estimating the difference.
#22: 81.656
75.285 + 2 + 3.871 + 0.5 = 81.656
#42: 0.0099
When you subtract 0.0001 from 0.01 you get 0.0099(remember, when you subtract 0.01 is the bigger number so you put that one on top because it has less zeros on the left, but when it has less zeros on the right it doesn’t change the value)
#50: 4.37
9.00 - 4.63 = 4.37
Hopefully this helps you!