4.解方程组$\left\{\begin{array}{l} 2025x-2026y= 2024\enclose{circle} {1},\\ 2024x-2023y= 2025\enclose{circle} {2}.\end{array}\right. $

$\left\{\begin{array}{l} x=2,\\ y=1\end{array}\right. $

5.解方程组:
(1)$\left\{\begin{array}{l} \frac {x}{2}= \frac {y}{3}\enclose{circle} {1},\\ 4x-3y= 3\enclose{circle} {2};\end{array}\right. $
(2)$\left\{\begin{array}{l} x:y= 3:2\enclose{circle} {1},\\ y:z= 2:1\enclose{circle} {2},\\ x+y+z= 60\enclose{circle} {3}.\end{array}\right. $

(1)$\left\{\begin{array}{l} x=-6,\\ y=-9\end{array}\right. $ (2)$\left\{\begin{array}{l} x=30,\\ y=20,\\ z=10\end{array}\right. $

6.解方程组$\left\{\begin{array}{l} 3(x+y)-4(x-y)= 8,\\ \frac {x+y}{3}+\frac {x-y}{12}= 3.\end{array}\right. $

$\left\{\begin{array}{l} x=6,\\ y=2\end{array}\right. $