You can
put this solution on YOUR website!Stand on the number line at the position of the first number, namely -10. Now you move 7 numbers, but you must go to the left because it is -7.
The other way to look at it is that you NEVER subtract, you always add the negative, thus:
(-10) - 7 is the same as (-10) + (-7) and it should be fairly clear that the sum of these two is -17.
Hope that helps.