2A. Jane read five books. From these five books, 5 sets of four books can be formed. The four books in each of these sets together had 913, 973, 873, 1011, and 1002 pages. How many pages did each of the five books have?
Solution. If the number of pages of 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 and divide by 4, we get $a+b+c+d+e=1193$. If we subtract each of the five equations from this equation, we obtain

$$
a=182, b=191, c=320, d=220, e=280 \text { pages. }
$$

3AB. Simplify the expression:

$$
\frac{x+1}{x-1}-\frac{2 x-6}{3 x-3} \cdot\left(\frac{x+1}{x-2}-\frac{2 x+3}{x-3}+\frac{x^{2}+4 x-9}{x^{2}-5 x+6}\right)
$$