Answer:
The answer is 15 units.
Explanation:
This is the Pythagorean theorem (a^2+b^2=c^2).
We can see that from A to C it is 9 units down. We also know that from C to B it is 12 units long. Using the Pythagorean theorem, we square both numbers, then add them, then take the square root.
9x9=81
12x12=144
144+81=225
The square root of 225=15 *since 15x15=225)*
Therefore A to B is 15 units long!