Verified answer

7

3x^2 - 12x <=0

3x(x - 4) <=0

++++++++++[0] --------------- [4] ++++++++++

x∈[0  4]

8

5x - 7x^2 > 0

x(5 - 7x) > 0

------------ (0) ++++++++ (7/5) ----------

x∈(0  7/5)

9

3x^2 < 10x

3x^2 - 10x < 0

x(3x - 10) < 0

++++++++++ (0) ------------- (10/3) +++++++

x∈(0     10/3)