The ratio of the height (h) of the streetlight to its distance to the end of Laura's shadow is the same as the ratio of Laura's height to her distance from the end of her shadow.
.. h/(12+9) = 5'4"/9
.. h = (21/9)*5'4" = 12 4/9 feet
.. h = 12 ft 5 1/3 inches
The streetlight is 12 ft 5 1/3 inches tall.
