I’m confused about what I did wrong in the procedure because I
should get 0.75 as a result.

A uniform board with a mass of 22 kg and a length of 8.5 meters rests horizontally on two supports. One support is 1.4 meters from the left end of the board. The amount of the normal force produced by the support on the left is 54 Newtons. Then, a person with a mass of 28 starts to walk towards the right end of the board. How far, in meters, from the right end of the board can he walk, before the board starts to come off the left support and rotate around the right support causing the person to fall off the board?