Hello!
The answers are:
Why?
For the first question, if there is no printed book, the variable x will be 0, so:
![y=1200+15x\\y=1200+15(0)](https://img.qammunity.org/2020/formulas/mathematics/college/7o5sgh05sos64d5o19997hcyi4hs59co8o.png)
The cost to get started, meaning that there is not any printed book, is $1200
For the second question, to determine the change in the total cost for each printed book, let's assume that there is just one book printed, so:
![y=1200+15x\\y=1200+15(1)=1215](https://img.qammunity.org/2020/formulas/mathematics/college/1gqj7vw9imy5nmkwdjtdvui5abp515bqcz.png)
So, the change for each printed book is $15(+) because:
![Change=(1)BookPrintedCost-NoBookPrintedCost=1215-1200=15](https://img.qammunity.org/2020/formulas/mathematics/college/2fimll5v9dg2omilrbcovpdmxh8ftv2glg.png)
Have a nice day!