2B. Jane read five books. From these five books, 5 sets of four books can be formed. The four books in each of these sets had a total of 913, 973, 873, 1011, and 1002 pages. How many pages did each of the five books have?
Solution. If the number of pages in the books are $a, b, c, d, e$ respectively, then we need to solve the system of equations:

$$
\left\{\begin{array}{l}
a+b+c+d=913 \\
a+b+c+e=973 \\
a+b+d+e=873 \\
a+c+d+e=1011 \\
b+c+d+e=1002
\end{array}\right.
$$

If we add all the equations, we get:

$$
\begin{aligned}
& 4(a+b+c+d+e)=4772 \\
& a+b+c+d+e=1193
\end{aligned}
$$

If we subtract each of the five equations from this equation, we get $a=182, b=191, c=320, d=220, e=280$ pages.