When adding and subtracting with small numbers I think it is normally helpful to think of temperatures - you could sketch a number line (like a thermometer) and use that to count on or count backwards. 

With this model of negative numbers, - is cold/colder (-3 is three degrees cold), + is hot/hotter (+5 is five degrees hot), and then if we have two signs between digits + is more and - is less. 

e.g.

3 + - 5 = temperature starts at 3 degrees and then becomes more cold by 5 degrees = 3 - 5 = 3 - 3 - 2 = -2

2 - - 6 = temperature starts at 2 degrees and then becomes less cold by 6 degrees

           = temperature starts at 2 degrees and then becomes hotter by 6 degrees = 2 + 6 = 8

- 7 - + 10 = temperature starts at -7 degrees and then becomes less hot by 10 degrees = 

               = temperature starts at - 7 degrees and then becomes colder by 10 degrees = - 7 - 10 = -17

Thank you so so so much! This is very helpful!