Box B = 1 unit, Box A = 4 units, Box C = 1 unit + 208 (208 more than B). The three boxes total 1450.

Box B1Box A1111Box C12081450

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

  1. 1 + 4 + 1 = 6 units, plus 208 → 1450
  2. 6 units → 1450 − 208 = 1242
  3. 1 unit → 1242 ÷ 6 = 207
  4. A − C = 4 units − (1 unit + 208) = 3 units − 208 = 621 − 208 = 413

There are 413 more beads in Box A than in Box C.

Check: B 207 + A 828 + C 415 = 1450. ✓