Answer: Choice A) -8-10
This can be written as -8 + (-10). Subtracting a positive is the same as adding a negative.
One way to think of negatives is to think of debt in money. Writing -8 means you are 8 dollars in debt. Add on 10 more dollars of debt and you'll be 8+10 = 18 dollars in debt total. So this is one way to see how -8-10 = -8+(-10) = -18.
Or you can think of it as if you are in a submarine. The number -8 could represent the idea you are 8 miles below sea level. Then if we subtract 10 from this, or add on -10, it means we're going down another 10 miles to get a total depth of 18 miles below sea level. At this point, we would write -18.
