Fatimah = 8 units, Siti = 11 units. Siti has 3 units more, and that difference is 9 cards.

Fatimah11111111Siti111111111119 more = 3 units

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

  1. Siti − Fatimah → 11 units − 8 units = 3 units → 9
  2. 1 unit → 9 ÷ 3 = 3
  3. Total → 8 + 11 = 19 units = 19 × 3 = 57

There were 57 cards in the pack.

Check: Fatimah 24 + Siti 33 = 57; 33 − 24 = 9. ✓