plain and short, you simply divide 32 by (5+3) and give 5 of those pieces to one side and 3 to the other, let's do so
[tex]\bf 5:3\qquad \cfrac{5}{3}\qquad \cfrac{5\cdot \frac{32}{5+3}}{3\cdot \frac{32}{5+3}}\implies \cfrac{5\cdot 4}{3\cdot 4}\implies \cfrac{20}{12}\implies 20:12[/tex]
