Adding integers with different signs: -3 + (-7)

Okay so in school I am doing this litterly right now. So all u have to do is when it is a different sign you subtract, when it is the same you add. So think of it as, Different/Difference and Same/Sum. when the sign is different u find the difference and when u have the same sign you find the sum. 
Example 1: -3+8= 5
Use the same sign as the largest number
Example 2: 5+(-10)= -5
Hopefully This helped! It is easier then you may think once you get the hang of it! ( You get the hang of it REALLY fast ) :)

The number in brackets is negative -
The number outside the bracket is positive... +
-x+ is - (a negative times a positive is a negative)
So you end up with
-3-7=?
Since they are both negative -
It stays negative along the negative line
-10 is the answer
IF it was -3-(-7) (negative times a negative is a positive)
Then it would have been -3+7
Which would carry it it back to positive because the + is with the bigger number
So -3+7 is 4
Hope this helped