8、公鸡一，值钱五；母鸡一，值钱三；鸡雏三，值钱一。百钱买百鸡，问公鸡、母鸡、鸡雏各几何
for (int i = 0; i <= 20; i++)
{for (int j = 0; j <=34; j++)
{for (int c = 0; c <= 100; c++)
{if (i*5+j*3+c/3==100&&i+j+c==100&&i%3==0)
{Console.WriteLine("公鸡{0},母鸡{1},小鸡{2}",i,j,c);}}}}
9、我有鸡和兔共 30 只，它们脚的个数共 90 只，所有鸡和兔都正常，问鸡和兔子各有几只？
for (int i = 0; i < 30; i++)
{for (int j = 0; j < 30; j++)
{if (i*2+j*4==90&&i+j==30)
{Console.WriteLine("鸡{0},兔{1}", i, j);}}}
10、乘法表
for (int i = 1; i <= 9; i++)
{for (int j = 1; j <= i; j++)
{Console.Write(j+"*"+i+"="+i*j+"\t");}
Console.WriteLine();}