$$\left. \begin{array} { l } { a = 3 , b = 5 c = 10 , v } \\ { a \times ( b + c ) = a b + a c } \\ { a = 84 b = 4 } \end{array} \right.$$
$a=3$
$b=5c$
$c\in \mathrm{C}$
$a=3$
$b=5c$
$c\in \mathrm{R}$
