First add the blue which is 2 + 4 and 2 +4 is 6. Then we have to add the next bar which is -8. 6 + (-8) . When you add a positive number and a negative number you are going to have to subtract. So 8-6 is 2. To determine if 2 is going to be a positive 2 or negative 2 you have to look at the bigger number which is 8, and 8 has a negative number. So you put the negative sign in the 2 which becomes -2.
