Ta có:
A = $10\frac{5}{7}$ x (-0,7) = $\frac{75}{7}$ x $\frac{-7}{10}$ = $\frac{-75}{10}$ = -7,5.
B = $2\frac{4}{5}$ / (-0,4) = 2,8 / (-0,4) = -7;
C = (-4,5) x $1\frac{31}{45}$ = $\frac{-45}{10}$ x $\frac{76}{45}$ = $\frac{-76}{10}$ = -7,6.
Do -7,6 < -7,5 < -7 nên ta có: C < A < B.