Respuesta:
a) [tex]\frac{2}{3}[/tex]
b) [tex]-\frac{4}{3}[/tex]
Explicación paso a paso:
a) Procedimiento:
[tex]\left(1+\frac{3}{4}\right)\frac{8}{21}\\\\1+\frac{3}{4}\\\\=\frac{1\cdot \:4}{4}+\frac{3}{4}\\\\=\frac{1\cdot \:4+3}{4}\\\\=\frac{7}{4}\\\\=\frac{7}{4}\cdot \frac{8}{21}\\\\=\frac{2}{3}[/tex]
b) Procedimiento:
[tex]-\left(\frac{2}{3}+\frac{5}{6}\right)\div \frac{9}{8}\\\\\frac{2}{3}+\frac{5}{6}\\\\=\frac{4}{6}+\frac{5}{6}\\\\=\frac{4+5}{6}\\\\4+5=9\\\\=\frac{9}{6}\\\\=\frac{3}{2}\\\\=-\frac{3}{2}\div \frac{9}{8}\\\\=-\frac{3}{2}\cdot \frac{8}{9}\\\\=-\frac{3\cdot \:8}{2\cdot \:9}\\\\2\cdot \:9=18\\\\=-\frac{24}{18}\\\\=-\frac{4}{3}[/tex]
