1st gift shop:
120/4 = 30 cents each
180/6 = 30 cents each
390/13 = 30 cents each
2nd gift shop:
204/7 = 29.14 cents each
192/8 = 24 cents each
270 /9 = 30 cents each
360/10 = 36 cents each
so if both gift shops have a fixed price then the 9 post cards would be the answer since it matches 30 each like the 1st gift store
The answer to this, maybe.., is 180
There are no restrictions on the domain of the since function.
The domain is all real numbers.