First piece = 43 cm.<br>
First piece is 5 cm longer than the second piece.<br><br>
&bull; Second piece = First &minus; 5 = 43 &minus; 5 = 38 cm<br>
&bull; Third piece is 9 cm shorter than the second piece.<br>
&bull; Third piece = Second &minus; 9 = 38 &minus; 9 = 29 cm<br>
<br>
The length of the third piece is 29 cm.<br>
Check: First 43, Second 38, Third 29. Gap 1 = 5, Gap 2 = 9. ✓