Answer:
The system of equations are
x+y=557

The total pages in shorter book is 245
The total pages in longer book is 312
Step-by-step explanation:
Given that,
Scott has read 407 of the total number of 557 pages, which
of the shorter book and
of longer book.
Total number of pages of shorter book be x and longer book be y.
Then,
page of the shorter book 
pages of the longer book = 
So, he has read 
Total number of pages of both book is = x+y
According to the problem,
x+y=557.........(1)
.......(2)
We can write equation (2) as



......(3)
Now 18 times of equation (1) subtract from equation (3)
18x+25y=12210
18x+18y=10026
- - -
_______________
25y-18y=12,210-10,026
⇒7y=2,184

⇒y= 312
Plug y=312 in equation (1)
x+312=557
⇒x=557-312
⇒x=245
The total pages in shorter book is 245
The total pages in longer book is 312