Let a * * * have x parts.

According to the meaning of the question: x ÷ (x ÷15+x ÷ 20) × (x ÷15-x ÷ 20) = 80.

Solution: x=560

Method 2: Arithmetic method

As can be seen from the meaning of the question, the ratio of the master's speed to the apprentice's speed is 4:3, then the ratio of the apprentice to the cooperation speed is 3:7, then the ratio of the apprentice to the cooperation time is 7:3, then the cooperation time is equal to 20÷7×3=60/7, and since the master has done 80 times more than the apprentice in the cooperation time, we can calculate how many times the master has done more than the apprentice every day.