12:8:4 = 39:A:B what is A and B

12:8:4 = 39:A:B what is A and B

$$\\\small{\text{$ \begin{array}{rclcrcl} 12\cdot \frac{8}{12} &=& 8 &\rm{~~or~~}& 12\cdot \mathbf{\frac{2}{3}} &=& 8\\\\ && &\rm{~~so~~}& 39\cdot \mathbf{\frac{2}{3}} &=& A\\\\ &&&&\textcolor[rgb]{1,0,0}{A}&\textcolor[rgb]{1,0,0}{=}& \textcolor[rgb]{1,0,0}{26}\\\\ \hline &\\ 8\cdot \frac{4}{8} &=& 4 &\rm{~~or~~}& 8\cdot \mathbf{\frac{1}{2}} &=& 4\\\\ && &\rm{~~so~~}& A\cdot \mathbf{\frac{1}{2}} &=& B\\\\ &&&& 26\cdot \mathbf{\frac{1}{2}} &=& B\\\\ &&&&\textcolor[rgb]{1,0,0}{B}&\textcolor[rgb]{1,0,0}{=}& \textcolor[rgb]{1,0,0}{13} \end{array} $}}$$

8 is 2/3 of 12.....so A is 2/3 of 39 = 26

4 is 1/3 of 12 .......so  B = 1/3 of 39 = 13