题目解二元一次方程组:(1){2x+y=1x−y=2\left(1\right)\left\{\begin{array}{l}2x+y=1\\ x-y=2\end{array}\right.(1){2x+y=1x−y=2；(2){3(x−y)=2xx−12=y\left(2\right)\left\{\begin{array}{l}3\left(x-y\right)=2x\\ \frac{x-1}{2}=y\end{array}\right.(2){3(x−y)=2x2x−1=y.知识点：解二元一次方程组——代入消元法章节：方程与不等式 / 二元一次方程组
