The question is interpreted in the following way.
The ratio of lights to bulbs is 3:5. The number of lights is 24 less than the number of bulbs, find the number of lights?
the number of lights be x,
the number of bulbs be y.
According to the task,
the system of equations is
It follows from the first equation that
Substituting for x into the second equation
Substituting for y=60 into the second equation
The number of lights is 36.