There are 2 people.
They will share 1 sandwich.
Thus, the sandwich (only 1) would be divided into 2 parts.
Each person will get 1 out of 2 parts.
We can write:
[tex]2x=1[/tex]Where "x" is the portion of sandwich one of them get. Solving for x >>>
[tex]\begin{gathered} 2x=1 \\ x=\frac{1}{2} \end{gathered}[/tex]Each gets half.