Answer
The researcher needs to sample another 62 adult Americans.
Work Step by Step
$p=0.10=10$%
We must have:
$np(1-p)\geq10$
$n0.10(1-0.10)\geq10$
$n\geq\frac{10}{0.10\times0.90}=111.111$
$n\geq112$ (The number of adult Americans must be an integer)
But, the researcher sampled 50 adult Americans. So, the researcher needs to sample another: $112-50=62$ adult Americans.
