2/5x+2/3(x-2/5x)+(2/5x- 1/3x)= x-30

You should be able to solve the equation, right? )

Finally x=225

The canal is 225 meters long.

(2)

First month: 2/5 × 225=90 (m)

Second month: 2/3 × (225- 2/5 × 225)=90 (m)

Third month: 2/5× 225-1/3× 225 =15 (m)

Answer: 90m was dug in the first month, 90m in the second month and15m in the third month.

Honey, I hope to adopt. I played it myself. )