just divide the 45 by the 4½
thus [tex]\bf 45\div 4\frac{1}{2}\iff \cfrac{45}{4\frac{1}{2}}\implies \cfrac{\frac{45}{1}}{\frac{4\cdot 2+1}{2}}\implies \cfrac{\frac{45}{1}}{\frac{9}{2}}\implies \cfrac{45}{1}\times \cfrac{2}{9}\implies \cfrac{45\times 2}{1\times 9}[/tex]
