Question

( fuvest - sp ) 5/3 - 7/9 é igual a:

A) 8/9
B) 22/9
C) 8/18
D) 2/3​

Answer 1

$\large\boxed{\begin{array}{l}\underline{\rm Subtrac_{\!\!,}\tilde ao\,de\,frac_{\!\!,}\tilde oes}\\\underline{\rm pelo\,m\acute etodo\,da\,borboleta.}\\\\\sf\dfrac{a}{b}+\dfrac{c}{d}=\dfrac{a\cdot d+b\cdot c}{b\cdot d}\\\\\sf\dfrac{5}{3}-\dfrac{7}{9}=\dfrac{5\cdot9-3\cdot7}{3\cdot9}\\\\\sf\dfrac{5}{3}-\dfrac{7}{9}=\dfrac{45-21}{27}\\\\\sf\dfrac{5}{3}-\dfrac{7}{9}=\dfrac{24}{27}\\\\\rm simplificando\,por\,3\,temos\\\sf\dfrac{5}{3}-\dfrac{7}{9}=\dfrac{24\div3}{27\div3}=\dfrac{8}{9}\end{array}}$