小明家的鸡下了7个蛋，小方家的鸡下了12个蛋，小丽家的鸡没下蛋。:c9s7x:G7]6l)g0I'E+N1a+J)U+]+_
（1）他们三家的鸡一共下了几个蛋？:c9s7x:G7]6l)g0I'E+N1a+J)U+]+_
算式：提示.{3~+a4[;s)Y-n;l;f.V*h:c9s7x:G7]6l)g0I'E+N1a+J)U+]+_
答：他们三家的鸡一共下了'v1r3e:O(y7L)[2e:o个蛋。:c9s7x:G7]6l)g0I'E+N1a+J)U+]+_
（2）小方家的鸡比小明家的鸡多下了几个蛋？:c9s7x:G7]6l)g0I'E+N1a+J)U+]+_
算式：提示9s*g2R3e;[;G,r-z.t;J*s:c9s7x:G7]6l)g0I'E+N1a+J)U+]+_
答：小方家的鸡比小明家的鸡多下了:g/O:?,r8Y-y'v5J7s2~0L(d-R个蛋。:c9s7x:G7]6l)g0I'E+N1a+J)U+]+_
（3）小明家的鸡比小丽家的鸡多下了几个蛋？:c9s7x:G7]6l)g0I'E+N1a+J)U+]+_
算式：提示7}8a1^'E4c:c9s7x:G7]6l)g0I'E+N1a+J)U+]+_
答：小明家的鸡比小丽家的鸡多下了8V'u.z-w,|2D个蛋。:c9s7x:G7]6l)g0I'E+N1a+J)U+]+_