Question 988438
"3 pieces were 12.8 feet long" 
3*12.8 = 38.4


"1 piece was 20.2 feet long"
total length of chain used up so far is 38.4+20.2 = 58.6 feet


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The chain is 150 ft, which leaves 150-58.6 = <font color="red">91.4 feet</font> of chain for the other project.