to add a decimal with a negative u must sub react them and If the negative is bigger than the positive than the negative over takes the positive and the awnser is negative.
You would need to start at -2.1 then go right 0.8 spaces and you would get -1.3 which is also the same as 2.1-0.8 because adding integers with different signs is the same as subtracting the two numbers. To determine the sign, the sign with the greatest number would be the sign. Since -2.1 is greater, your sign would be negative.
