Some students have difficulty using a number line because of right-left difficulties and the fact that there are some counter-intuitive principles when dealing with positive and negative numbers (the negative of a negative number is a positive).
What might make more intuitive sense is considering positive and negative numbers in terms of money.
-4 + – 10 = – 14
If I owe Dad 4 dollars and 10 dollars, then I owe him $14 in all.
-5 + 6 = 1
If I owe 5 dollars, but am given 6, then I have 1 dollar left over.
5 – -3 = 8
If I have $5 and a debt of $3 that is taken away, I have a credit of $8.
Want more real life examples of negative numbers? Check this from Scholastic.