## Precalculus (6th Edition) Blitzer

$\dfrac{78}{100}$
We see that there are a total of $100$ students in this survey and this can be our denominator. Also, there are $40$ students with brown eyes and $38$ students with blue eyes in this survey; this can be our numerator. This implies that we need $78$ students. That is, $\dfrac{78}{100}$