Vocab in your own words: How to add two positive integers:
How to add two negative integers:
How to add a positive and a negative integers:

How to add two positive integers:

You add the numbers like you normally would. There's no trick even though it seems like a trick question.

Example: 3+5 = 8

In that example, you can think of like starting at 3 on the number line. Then you move 5 units to the right to arrive at 8 on the number line.

How to add two negative integers:

Treat the negative numbers as their positive version of themselves. Next, you add those positive counterparts like normal. The last thing you do is make the result negative.

For example,

-9 + (-12) = -21

which we can think of like this

9+12 = 21

Then we just make everything negative to get that first equation mentioned.

How to add positive and negative integers:

This will depend on which has larger absolute value. In other words, which is further away from 0 on the number line.

In any event, you basically subtract the positive version of each number. Then the one furthest from 0 will determine if the result is positive or negative.

Examples:

-8 + 9 = 1

7 + (-12) = -5

In the first example, we can think of it like 9-8 = 1. I'm subtracting the two numbers 8 and 9, but doing so large - small and only focusing on the positive versions so far. Because 9 is further away from 0 compared to -8, this ultimately means the result is positive (since 9 is positive).

In the second example, we would say 12-7 = 5. Then note how -12 is farther away from 0 compared to 7. This means the negative side wins, so to speak, and the final result is negative.

answer: all of the odd numbers were opened

the first person was the one that was opening all of the lockers. since one is odd, this causes all of the odd number lockers to be opened in the end.