Which situation CANNOT be represented by this equation?

x + 7 = 31


Taliba has $31 to order phone cases online.
She buys 4 phone cases and pays a $7 shipping charge.
What is x, the cost of each phone case?


Taliba is ordering phone cases that cost $4 each online.
There is also a $7 shipping charge.
If she has $31 to spend, how many phone cases, x, can she buy?


Taliba has $31 to order phone cases online.
Each phone case costs $7, and there is a $4 shipping charge.
How many phone cases, x, can Taliba buy?