Yes that is correct or in other form, True
Efficiency is calculated through dividing the actual mechanical advantage by the hypothetical mechanical advantage:
- the actual mechanical advantage is 9J because that's how much work the light bulb doing
- the hypo. mechanical advantage is 100J. Ideally, in a perfect world, the light bulb can convert 100J input into 100J output, but do to resistance and other factors it is not possible.

change the decimal to a percentage:

the light bulb had 9% efficiency
Answer:
25%
Explanation:
use F=mg
then use the answer you get from that and plug it into W=Fxh
take that answer and divide it by 400 J and multiply by 100
round to sig figs