According to different topics, we can get n △ =1*1/2 *1/3 *. . . * 1/n So 7△/5△= 1 * 2 * 3 * 4 * 5/ 1 * 2 * 3 * 4 * 5 * 6 * 7 = 1/6 * 7 = 1/42。

X triangle = 1/40320 is mainly to see that several continuous numbers are multiplied by 40320, so divide 40320 by 1, 2, 3, 4. . . . Let's see how many times it has been divided, and the result is 1.

So 40320/1= 40320; 40320/2=20 160 ; 20 160/3=6720 ; 6720/4= 1680 ; 1680/5=336 ; 336/6=56 ; 56/7=8 ; 8/8= 1

So the solution is X=8.

Because of the input method, the symbol can only be marked △. Sorry, let's have a look ~