X=-7 is the solution.

8. It is assumed that X units are produced on average every day.

600/x=450/x-50

The result is x=200.

9. Set this harvester to harvest x hectares per hour.

( 10/x)+ 1 = 10/(x/ 150 * 100)

The result is x=5.

10. Let the speed of the previous hour be xkm/h.

180/x-2/3 = 1+ 180-x/ 1.5x

The result is x=60.