Solve the inequality: −7 ≤ x + 21 write your solution in interval notation.

You want all numbers from -∞ to ∞ except for the two numbers -3 and 3.  So you will have one interval that goes from -∞ to -3, (-∞,-3); a second interval from -3 to 3, (-3,3); and a third interval from 3 to infinity, (3,∞). I hope this helps!