Initial quantity = $50
Quantity already spent = $28
Want $5 or more leftover
If the intial quantity is $50 and you already spent $28, then you have 50 - 28 = 22
If you want to keep at least 5 then we can write:
x + 5 <= 22 ==> x <= 17
This means that the quatity you can spend plus 5 (leftover) has to be less than or equal to 22
Answer:
x <= 17
Where x is the quantity you can spend to keep at least $5
