用给出的四个数,用加减乘除及括号组成结果是24的算式(数字次序可以变动):2,8,9,13 ;3,7,9,13;

问题描述:

用给出的四个数,用加减乘除及括号组成结果是24的算式(数字次序可以变动):2,8,9,13 ;3,7,9,13;
3,4,6,13;2,4,6,7;1,3,4,8;3,3,9,9;1,2,3,5;2,2,4,5;
3,3,5,6; 2,6,9,9;1,5,5,5;2,4,10,10;3,3,7,7;3,3,8,8;
1,4,5,6;2,7,12,13;3,4,8,13;2,3,5,12;3,4,6,13;1,6,6,8;2,8,9,13;1,3,4,6;1,12,12,8;2,5,5,10;5,5,7,11;3,5,5,9;4,4,5,5;4,9,9,12;请附解题思路,

2x(13-9+8)=24