1. (-3) + (+5) = -3 = 5 = 2;
2. (+23) + (-13) = 23 - 13 = 10;
3. (-15) + (+15) = -15 + 15 = 0;
4. (-8 1/3) + (-3 5/6) = -8 1/3 - 3 5/6 = -8 2/6 - 3 5/6 = - 50/6 - 23/6 = -73/6 = -12 1/6;
5. (+5,3) + (-0,6) + (4,7)= 5,3 - 0,6 + 4,7 = 9,4;
6. (-3 1\8) + (+2,5) + (-3 3\8) = -3 1\8 + 2,5 - 3 3\8 = -25/3 + 7,5/3 - 27/3 = 5,5/3 = 55/30 = 1 25/30 = 1 5/6