$a < b$. Which of these is always true?

Explanation

1. 01

   Multiplying both sides by a negative number reverses the inequality: $a < b$ gives $-3a > -3b$.

2. 02

   The others fail: $-3 < 1$ but $9 > 1$; $a = -1$, $b = 1$ give reciprocals $-1$ and 1, still in the same order; and subtracting 5 keeps $<$.