Nilu covers a distance by walking for 6 h. While returning,

Nilu covers a distance by walking for 6 h. While returning, his speed decreases by 2km/h and he takes 9 h to cover the same distance. What was her speed while returning?

Let the speed in return journey = x
According to the question,
6( x + 2 ) = 9x
⇒ 6x + 12 = 9x
⇒ 9x - 6x = 12
⇒ 3x = 12
∴ x = 12/3 = 4km/h