Let us say that h is the height of the guardrail. Therefore the inequality equation that we can generate from this scenario is:
| h – 106 | = ± 7
There are two ways to solve this, either the equation is positive or negative.
When the equation is positive, therefore:
| h – 106 | = 7
h = 7 + 106 = 113 cm
When the equation is negative, therefore:
| h – 106 | = - 7
h = -7 + 106 = 99 cm
So the height must be 99 cm to 113 cm