Explicação passo-a-passo:
.
[tex] \dfrac{1}{5} + \dfrac{2}{7} [/tex]
[tex] \dfrac{7 + 10}{35} [/tex]
[tex] \dfrac{17}{35} [/tex]
.
[tex] \dfrac{3}{4} - \dfrac{1}{3} [/tex]
[tex] \dfrac{9 - 4}{12} [/tex]
[tex] \dfrac{5}{12} [/tex]
.
[tex] \dfrac{2}{9} \times \dfrac{5}{8} [/tex]
[tex] \dfrac{10 \div 2}{72 \div 2} [/tex]
[tex] \dfrac{5}{36} [/tex]
.
[tex] \dfrac{1}{3} \div \dfrac{2}{4} [/tex]
[tex] \dfrac{1}{3} \times \dfrac{4}{2} [/tex]
[tex] \dfrac{4 \div 2}{6 \div 2} [/tex]
[tex] \dfrac{2}{3} [/tex]
