well, clearly the LCD from the denominators of 5 and 10 is just 10, thus
[tex]\bf \stackrel{\textit{Sue}}{\cfrac{2}{5}}+\stackrel{\textit{Sally}}{\cfrac{4}{10}}\implies \stackrel{\textit{LCD of 10}}{\cfrac{(2)2~~+~~(1)4}{10}}\implies \cfrac{2+4}{10}\implies \cfrac{6}{10}\implies \stackrel{\textit{simplified}}{\cfrac{3}{5}}[/tex]
