Final answer:
Niki starts with 20 points, then loses 10 points and another 25 points, ending with -15 points, as visualized on a number line by moving left from her initial score.
Step-by-step explanation:
Niki's score changes in a card game can be tracked using a number line. She starts with 20 points, then she loses 10 points, bringing her score down to 10 points (20 - 10 = 10). Now from this point, if she loses an additional 25 points, her score would drop below zero to -15 points (10 - 25 = -15). This can be visualized on a number line by starting at 20, moving left (which denotes losing points) 10 spaces to reach 10, and then moving left again 25 spaces to end at -15.