\[
a < b \quad \text{ y } \quad b < c
\Rightarrow a < c
\]
\[
a < b \Rightarrow a + c < b + c
\]
\[
a < b \quad \text{ y } \quad c > 0
\Rightarrow ac < bc
\]
\[
a < b \quad \text{ y } \quad a > 0
\Rightarrow \frac{1}{b} < \frac{1}{a}
\]