Step-by-step explanation:
standard equation of sphere    , (x-a)²+ (y-b)²+( z-c)² = r² where a.b.c are the centre of the sphere r is radius and x,y,z are the coordintes of the point on the surface of the sphere
(x-7)²+( y-1)²+(z-1)²=16
x²+49-14x+y²+1-2y+z²+1-2z=16
x²+y²+z²-14x-2y-2z+35=0
(b) same as above diameter = 8 ,radius = 4 and centre is given
(c) (x-1)²+(y-3)²+(z-2)² = r²  it passes through (0,0,0)
      (0-1)²+( 0-3)²+(0-2)²=r²  ⇒ r =√14   now we have centre and radius same as above 
(d) centre is mid point of the end points of diameter
(1+0/2)=x   ,(2+2/2) =y   (1+3/2) =z ⇒   (x,y,z) = (1/2,2,2)  and 
 radius = distance between centre and any end points of the diameter
so radius =  √(1/2-1)²+(2-2)²+(2-1)²   =   √5/2 now we can find the equation of the sphere