Since the numbers that we are using are in the forms of tens, we can draw a simplified number line like
For the first problem, we are adding -30 to -20. This means that we will jump 3 times to the left since we are dealing with negative numbers. The jump is 3 times because each jump represents 10. Hence, this is described as
For the second part, we are adding +30 to -20. Since we are adding up a positive number to a negative number, we will jump 3 times to the right. This can be represented in the number line as
