Question 179087
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.