$3^o > 2^o > 1^o$

Thus the bromination of $2-$ methyl butane mainly gives $2-$ Bromo $-2-$ methyl butane

$\mathop {\begin{array}{*{20}{c}}
  {\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,C{H_3}} \\ 
  {\,\,\,\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,} \\ 
  {C{H_3} - C{H_2} - CH - C{H_3}} 
\end{array}}\limits_{2 - methyl\,bu\tan e} \xrightarrow{{B{r_2}}}$

$\mathop {\mathop {\begin{array}{*{20}{c}}
  {\,\,\,\,\,\,\,\,\,\,C{H_3}} \\ 
  {\,\,\,\,\,|} \\ 
  {C{H_3} - C{H_2} - CH - C{H_2}Br} 
\end{array}}\limits_{1 - Bromo - 2\,methyl\,bu\tan e} }\limits_{(\min or)} $ $+$ $\underset{\begin{smallmatrix} 
 2-Bromo-2-methyl\,bu\tan e \\ 
 \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(major) 
\end{smallmatrix}}{\mathop{\begin{matrix}
   \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,C{{H}_{3}}  \\
   \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|  \\
   C{{H}_{3}}-C{{H}_{2}}-C-C{{H}_{3}}  \\
   \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|  \\
   \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,Br  \\
\end{matrix}}}\,$