Given Two vertices of a triangle are (2, -6, 4), (4, -2, 3) and its centroid is (8/2,-1,3).

Let the third vertex (x, y, z)

Now,

     {(x + 2 + 4)/3, (y - 6 - 2)/3, (z + 4 + 3)/3} = {8/2, -1, 3}

=> {(x + 6)/3, (y - 8)/3, (z + 7)/3} = {4, -1, 3}

Now, (x + 6)/3 = 4

=> x + 6 =  3*4

=> x + 6 = 12

=> x = 12 - 6

=> x = 6

(y - 8)/3 = -1

=> y - 8 = -3

=> y = 8 - 3

=> y = 5

and (z + 7)/3 = 3

=> z + 7 = 9

=> z = 9 - 7

=> z = 2

So, the third vertex is (6, 5, 2)