Use the information given in the figure below to construct a mathematical model for the number of pounds of salt $x_1(t),x_2(t),$ and $x_3(t)$ at time $t$ in tanks $A,B,$ and $C,$ respectively.

$$

$\frac{d{x}_1}{dt}=\frac{2x_2-8x_1}{100}$

$\frac{d{x}_2}{dt}=\sqrt[\phantom{2}]{R_r-a_n+}$

$\frac{d{x}_3}{dt}=$

$$