Answer:
The efficiency is 84%.
Step-by-step explanation:
The efficiency is the percentage that it delivers, so it can be solved by a rule of three.
6.3 watts - x
7.5 watts - 1
[tex]7.5x = 6.3[/tex]
[tex]x = \frac{6.3}{7.5}[/tex]
[tex]x = 0.84[/tex]
So the efficiency is 84%.