Sure! Here's how you can fill in the blanks:
The population decreased by 2.
Use algebra tiles to represent the expression.
We're going to use a variable to represent the unknown quantity of the population.
Use the variable x.
Drag a positive x tile to represent the population.
Since I'm decreasing by 2, I am subtracting 2, so I have x - 2.
So the full statement would read: "Drag a positive x tile to represent the population. Since I'm decreasing by 2, I have x - 2."