For this case we have:
x: Let the variable representing the number of nachos
y: Let the variable representing the number of hamburgers
If you want to buy at least 5 items we have:

If you cannot spend more than $16 we have:

Thus, the inequality system is given by:

Possible solutions:
Now we have to buy 3 nachos and 2 hamburgers:

Is fulfilled!

Thus, you can buy 3 nachos and 2 hamburgers.
If you buy 2 nachos and 3 hamburgers:

Is fulfilled!

Is fulfilled!
Thus, you can buy 2 nachos and 3 hamburgers.
ANswer:

You can buy 3 nachos and 2 hamburgers.
You can buy 2 nachos and 3 hamburgers.