a) $\frac{-4}{8}$ = $\frac{-7}{x}$
⇔ -4x = -7.8
⇔ x=14
b) $\frac{-5}{y}$ = $\frac{20}{28}$
⇔$\frac{-5}{y}$ = $\frac{5}{7}$
⇔y=-7
c)$\frac{y}{7}$ = $\frac{6}{21}$
⇔$\frac{y}{7}$ = $\frac{2}{7}$
⇔y=2
d) $\frac{x}{5}$ = $\frac{-6}{10}$
⇔$\frac{x}{5}$ = $\frac{-3}{5}$
⇔x=-3
e) $\frac{-3}{y}$ = $\frac{33}{77}$
⇔$\frac{-3}{y}$ = $\frac{3}{7}$
⇔y=-7
f) $\frac{x}{7}$ = $\frac{6}{21}$
⇔ giống phần c
g)$\frac{11}{6}$ = $\frac{y-5}{-12}$
⇔$\frac{22}{12}$ = $\frac{5-y}{12}$
⇔5-y=22
⇔y=-18
