To break even, the equations must satisfy that
[tex]C(x)=R(x)\text{.}[/tex]Substituting the explicit form of the equations, we get:
[tex]50x+1600=66x\text{.}[/tex]Subtracting 50x, we get:
[tex]\begin{gathered} 50x+1600-50x=66x-50x, \\ 1600=16x\text{.} \end{gathered}[/tex]Dividing by 16, we get:
[tex]\begin{gathered} x=\frac{1600}{16}, \\ x=100. \end{gathered}[/tex]Answer:
[tex]100\text{ units.}[/tex]