You can
put this solution on YOUR website!Let the number of reprints =

Let cost =

Local photo shop:

(in cents)
Through mail:

When is th3e cost of the reprints through the mail less?

Subtract

from both sides

Divide both sides by

Or, writing it in the other direction,

mail order is less expensive if 16 reprints are ordered
check:
what is each way for 15 reprints?

and

OK
Now check each way for 16 reprints