A: Omit.

(3) If there are X apprentices, then the master will do (2x- 10), which means (2x- 10)-x=290.

2x- 10-x=290，

x=300

2x- 10=590

A: Omit.

(2) If the pineapple is X Jin, the banana is (x+84) Jin.

x+x+84=386

2x=302

x= 15 1

x+84=235

A: Omit.

(1) If the walking speed is x km/min, the riding speed is 3x km/min.

20(x+3x)=6.4

80x=6.4

x=0.08

3x=0.24

A: Omit.