#### Answer

The required inequality is $20x+10y\le 80,000$.

#### Work Step by Step

We know that the number of water bottles and medical packets is $x\text{ and }y$, respectively.
Then, according to the statement given, a plane can carry a maximum weight of $80,000$ pounds. Therefore, the required inequality will be as given below:
$20x+10y\le 80,000$
Thus, the required equation is $20x+10y\le 80,000$.