We have the following:
We have the following equations
Dudley Photography

Lasting Memories Company

Where x is the number of portrait sheet
Now, to calculate when the cost will be the same in any study, we must equalize the equations in the following way
D = L
replacing:

solving for x:

Which means that at 2 portrait sheets the cost is the same.
Now, we calculate the cost:

The cost is $110