What's in the lucky draw?

Solution: (1) Draw a tree diagram: As can be seen from the above, there are exactly six situations drawn by H 2, (W 1, H 2, S 1), (W 1, H 2, S 2); ，(W 2，H 2，S 65438+。

(2) There are three cases where the sum of subscripts in ∫ from (1) is 7.

∴ The probability that the sum of subscripts of tag codes drawn by Liang Xiao (for example, the subscript of "W 2" is "2") is 7 is: =.