Answer
It would take $10$ seconds for the sound of thunder to reach us.
Work Step by Step
Using the information given, we know that we are $2$ miles from the lightning flash, but we want to know how long it will take the sound of thunder to reach us.
We use the formula given and plug in $2$ for $M$:
$2 = \frac{n}{5}$
We want to solve the equation for $n$, the number of seconds it takes for us to hear the sound of thunder.
To solve for $n$, we multiply both sides of the equation by $5$ to get rid of the fraction:
$n = (2)(5)$
$n = 10$
It would take $10$ seconds for the sound of thunder to reach us.
