[tex]\it Fie \ \ s\ -\ suma\ ini\c{\it t}ial\breve a\ .\\ \\ \dfrac{1}{3}s\ (cost\breve a\ chitara);\ \ rest\ \ \dfrac{2}{3}s\\ \\ \\ \dfrac{1}{\not2}\cdot\dfrac{\not2}{3}s=\dfrac{1}{3}s\ (cost\breve a\ \ microfonul);\ \ rest\ \dfrac{1}{3}s[/tex]
[tex]\it \dfrac{1}{4}\cdot\dfrac{1}{3}s=\dfrac{1}{12}s\ \ (cost\breve a\ flautul) ;\ \ rest\ \dfrac{^{4)}1}{\ 3}s-\dfrac{1}{12}s=\dfrac{\ 3^{(3}}{12} s=\dfrac{^{25)}1}{\ \ 4}s=\\ \\ \\ =\dfrac{25}{100}s=25\%\ din\ s\ (au\ r\breve amas\ la\ final)[/tex]
