2.8x=20×4.2
x=30
Question 2: I really can't think of it.
Question 3:1+100 =101.
Powder: 4040 ÷ 10 1 = 40 (kg) Water: 4040 ÷10100 = 4000 (kg).
Question 4: Desk: 30× 3 = 90 yuan Chair: 30× 2 = 60 yuan.
I'm exhausted, please adopt!