Answer: 27 units
Step-by-step explanation:
The y coordinates are the same. Focus on the x coordinates only.
Let A = -18, B = 0 and C = 9. Plot these values on a number line.
The gap from A to B is 18 units. The gap from B to C is 9 units.
The total distance from A to C is therefore 18+9 = 27 units.
An alternative method is to use the distance formula, but it's a bit overkill in my opinion.