For this case, we can solve the problem by using the following ratio:
[tex]\frac {25} {1} = \frac {x} {5}[/tex]
Where,
x: number of letters in 5 minutes
Clearing the value of x we have:
[tex]x = 5 (\frac {25} {1})\\x = 5 * 25\\x = 125[/tex]
Answer:
At that rate, the number of letters that the worker can stamp in 5 min is 125.
Option D.