1 pear box = 160- 140=20 (kg)

1 box of apples =(80-3x20)÷2= 10 (kg) ┃ More details below ┃

12 flour and 20m =4x2 10=840 (kg)

12 flour and 9m =3x 170=5 10 (kg)

1 1 rice =840-5 10=330 (kg)

1 m =330÷ 1 1=30 (kg)

3m =3x30=90 (kg)

4 Flour = 170-90=80 (kg)

1 flour =80÷4=20 (kg)