12.“今有鸡兔同笼,上有24头,下有74足,问鸡兔各几何?”设鸡有x只,兔有y只,则下列方程组中正确的是( )
0 284864 284872 284878 284882 284888 284890 284894 284900 284902 284908 284914 284918 284920 284924 284930 284932 284938 284942 284944 284948 284950 284954 284956 284958 284959 284960 284962 284963 284964 284966 284968 284972 284974 284978 284980 284984 284990 284992 284998 285002 285004 285008 285014 285020 285022 285028 285032 285034 285040 285044 285050 285058 366461
| A. | $\left\{\begin{array}{l}{x-y=24}\\{2x+4y=74}\end{array}\right.$ | B. | $\left\{\begin{array}{l}{x-y=24}\\{4x+2y=74}\end{array}\right.$ | C. | $\left\{\begin{array}{l}{x+y=24}\\{2x+4y=74}\end{array}\right.$ | D. | $\left\{\begin{array}{l}{x+y=24}\\{4x+2y=74}\end{array}\right.$ |