The table is one unit (= the chair) plus an extra 3 kg. Together they are 21 kg.

Chair?Table?321 kg

Plain numbers are given; italic underlined numbers are worked out.

  1. 2 units + 3 → 21 kg
  2. 2 units → 21 − 3 = 18 kg
  3. 1 unit (chair) → 18 ÷ 2 = 9 kg
  4. Table → 9 + 3 = 12 kg

The table is 12 kg.

Check: 12 + 9 = 21 kg, and 12 − 9 = 3 kg. ✓