Answer is A m^7/n^2 -----------------
......................... 1/2
Three times the difference of a number n and 1
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
Your equation is correct.
