I am having difficulties determining if this relation is reflexive, symmetric, transitive, or none of these.
Let A be the set of all strings of $0's$, $1's$, and $2's$ of length $4$. Define a relation $R$ on $A$ as follows: For all $s$, $t ∈ A$, $s$ R $t$ if and only if the sum of the characters in s equals the sum of the characters in t.
Examples this is true:
$0121$ R $2200$
$1220$ R $2111$