Firstly, lets subtract the sales tax to make things easier. This leaves us with 121.29
Now lets subtract the cost of the camera, giving us $29.31
The cost of the case is 1/6 of the camera, so 91.98/6=$15.33
Subtracting this leaves us with $13.98
This is what the two memory cards cost, so we can divide this by two to find the cost of one, $6.99