Four Fours/13/Mistake

Source Work

 * Four Fours
 * Solution
 * Solution

Mistake

 * The writer added the following postscript: "Another simple solution for $13$ is: $13 = \dfrac {4!} 4 + \dfrac 4 4$."

In fact $\dfrac {4!} 4 + \dfrac 4 4 = 7$.

It is probable that the above is a misprint for this solution: