Red = 1 unit, purple = 3 units, yellow = 3 units + 41. The three bars total 545 marbles.

Red1Purple111Yellow11141545

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

  1. 1 + 3 + 3 = 7 units, plus 41 → 545
  2. 7 units → 545 − 41 = 504
  3. 1 unit → 504 ÷ 7 = 72
  4. Yellow − Red = 2 units + 41 = 144 + 41 = 185

There are 185 fewer red than yellow marbles.

Check: red 72 + purple 216 + yellow 257 = 545. ✓