Answer:72 bulbs
Explanation:
Given
Ratio of defective light bulbs produced to total light bulbs produced is about
3:500
that is if 503 bulbs are manufactured then 3 are defective
let x be the non-defective bulbs in 12000 bulbs
defective bulbs=

therefore
12000=Non-defective +defective



Therefore Defective bulbs =12000-11928=72 bulbs