In order to make the given transformation (rotation of 180°) you consider thatsuch transformation demands:
T(x,y) => (-x,-y)
Then, when you apply the previous transformation to the points L(2,6), M(8,8) and K(7,4), you obtain:
T[L(2,6)] => L'(-2,-6)
T[M(8,8)] => M'(-8,-8)
T[K(7,4)] => K'(-7,-4)