Answer :
Hey there!
First of all, we see that each backpack sold gives a profit of $20. We see the word at least in the equation, so that means that we will use this type of inequality.
backpacks sold ≥ #
We can plug our info into an inequality and solve, with b being the number of backpacks sold.
20b-11,000≥7,800
20b≥18800
b≥940
I hope that this helps! Have a great day!