7x - 6 + 3x + 12 = 16

Sample Response: Although 6 and 3 are on opposite sides of sea level, or 0, they are not opposites because they are unequal distances from 0.

Step-by-step explanation:

3 is 3 units above 0 on a vertical number line.

–6 is 6 units below 0 on a vertical number line.

3 is not the opposite of –6.

Opposites are equal distances from 0.