48X=(48+2)(X- 1)

X=25

25×48= 1200

2.945-(2+5)* 15=840 (1) Thinking method: 2+5+5 hours are all regarded as apprenticeship production, minus.

840/(2+5+5)=70 (pieces) The first step of production takes more than 7 hours. The remaining 840 yuan.

70*5=350 (a) apprentices are born in "12" hours, so divide by 12, which is

(70+ 15)*7=595 (pieces) is the second step. You should be able to understand the following, so don't say it.

Equation: If the apprentice does not produce X per hour, then the master produces X+ 15 per hour.

2(X+ 15)+5(X+X+ 15)= 945

X=70

5X=350，(2+5)(X+ 15)=595

3. Master-apprentice cooperation.

15-5 = 10 days

Guide the cooperation to be completed within 10 days.

12+0× 10 = 5/6.

The apprentice finished it in five days.

1-5/6 = 65438/6+0

Apprentices finish it every day.

1 ÷ 5 = 1 = 30.

Master finishes it every day.

12 1-30 1 = 20 1

If this batch of parts was completed by the master alone,

1/20 1 = 20 days