Question

The office worker can stamp 25 letters per minute.

Answer 1

For this case, we can solve the problem by using the following ratio:

$\frac {25} {1} = \frac {x} {5}$

Where,

x: number of letters in 5 minutes

Clearing the value of x we have:

$x = 5 (\frac {25} {1})\\x = 5 * 25\\x = 125$

Answer:

At that rate, the number of letters that the worker can stamp in 5 min is 125.

Option D.

Answer 2

You set it up into a fraction equation. 25 over 1 = x over 5. The numerator is the letters and the denominator is the minutes. You then cross multiply and then you get x=125. That is your answer. Hope that helps.