Let each person get portion "x".
So, 3 person would get "3x" and that would be equal to "1" sandwich.
Thus, we can write the equation:
[tex]3x=1[/tex]Let's solve for "x",
[tex]\begin{gathered} 3x=1 \\ x=\frac{1}{3} \end{gathered}[/tex]Each person will get one-third of a sandwich.