Different kinds of numbers are used to stand for different things. There are positive numbers and there are negative numbers.
Positive numbers are more than zero and negative numbers are less than zero.
The answer is 1. To add a positive to a negative, you work from left to right. You get that by starting at -4 and moving three places to the right. To add two negatives, move to the left. You arrive at that answer by starting at -1 and counting three places to the left .