The question asks for the number of proper subsets of the set $L$, which contains the best-dressed men of 2015. The members of the set $L$ are listed:

$L = \{ \text{Tom Hiddleston}, \text{Robert Pattinson}, \text{David Beckham}, \text{Benedict Cumberbatch}, \text{Henry Cavill}, \text{Tinie Tempah}, \text{Zac Efron} \}$

The cardinality (size) of the set $L$ is 7, since there are 7 elements in the set.

Number of subsets:

For any set with $n$ elements, the total number of subsets (including both proper and improper subsets) is given by: $2^n$ So, for $L$, the total number of subsets is: $2^7 = 128$

Proper subsets:

Proper subsets are all subsets except the set itself. Therefore, the number of proper subsets is: $2^7 - 1 = 128 - 1 = 127$

Thus, the number of proper subsets of $L$ is 127.

If you would like further explanation or have any questions, feel free to ask!

Here are 5 related questions:

1. What is the difference between a proper and an improper subset?
2. How many subsets would a set with 5 elements have?
3. Can a set have an infinite number of subsets?
4. What is the formula for finding the number of subsets of any set?
5. What is the cardinality of the power set of $L$?

Tip: Always remember that a proper subset of a set cannot be the set itself!