Question 6
Let $A$, $B$, $C$ and $D$ be four distinct positive integers such that
$$\frac1A+\frac1B+\frac1C+\frac1D=\frac{21}{22}.$$
What are all possible values of $A+B+C+D$?
$$\frac1A+\frac1B+\frac1C+\frac1D=\frac{21}{22}.$$
What are all possible values of $A+B+C+D$?