Let d = number of days.
$21 per day is represented by 21d.
A fixed fee of $48 is simply 48.
The total cost is 21d + 48.
The total cost for last month was $426, so we let our cost expression equal 426 giving us the equation
21d + 48 = 426
Now we solve for d.
Subtract 48 from both sides.
21d = 378
Divide both sides by 21.
d = 18
Since we let variable d represent the number of days, we conclude that Olive spent 18 days at the daycare.
Answer: A. 21d + 48 = 426; 18 days
