Answer
The sum of the first roll was -3, and the sum of the second roll was 4.
Work Step by Step
Since we have two cubes, one to represent a positive value and one to represent a negative value, we could get either a positive, negative, or zero value for the x-coordinate and y-coordinate.
Since the x-coordinate is -3, the sum of the two cubes shows the negative cube had a higher absolute value than the positive number cube. For example:
$$-6+3=-3$$
Similarly, the y-coordinate is 4, so the positive cube had a higher absolute value. For example:
$$-1+5=4$$
