Sir I am unable to understand that how you find the value of v in hypermetropia and myopia

Myopia is a defect of vision in which a person clearly sees all the nearby objects, but is unable to see the distant objects comfortably and his eye is known as a myopic eye.

 A myopic eye has its far point nearer than infinity. It forms the image of a distant object in front of its retina as shown in the figure.

So, for the correcting concave lens.

Object distance, u =

Image distance, v = person’s far point (so, that person is able to see all the objects beyond this far point)

Concave lens makes image of the objects at infinity at a point which is the far point of the person. 

Same thing is done for the case of  hypermetropic eye.