The speed of light (electromagnetic radiation) is equal to 299 792 458 m / s or 3x10^8 m/s in scientific notation.
So with this information, we could now look for the distance. Solution:
Take note that μs means microseconds.
Speed of light * microseconds travelled * actual amount of microseconds
(3x10^8 m/s) (45.0 μs) (1x10^-6 s/μs) = 13,500 m.