When you go left on a number line, you are going to go to further into the negatives.
<--- Negative or Positive --->
-10_-9_-8_-7_-6_-5_-4_-3_-2_-1_0_1_2_3_
Since you want to go 7 units to the left, The answer would be -8. You should recount on the number line just to double check.