Let's assume the cost of each bag of lemons is x dollars.
Since Robert buys 5 bags of lemons and each bag costs the same amount, the total cost of the lemons is 5x dollars.
The total amount Robert pays is the sum of the cost of the cheese and the cost of the lemons, which is $5.31 + 5x dollars.
According to the problem, Robert pays a total of $24.36.
So we can write the equation:
$5.31 + 5x = $24.36
Now, let's solve for x.
Subtract $5.31 from both sides of the equation.
5x = $24.36 - $5.31
5x = $19.05
Divide both sides of the equation by 5.
x = $19.05 / 5
x = $3.81
Therefore, each bag of lemons costs $3.81.