Question 1063730
You know focus and vertex.  The directrix is the line  16-7=9  units away from the vertex, but on the other side of the vertex than the focus.  The directrix is the line  {{{x=-2}}}.
You also call this the point  (-2,y).


Look in your book for the definition of a parabola, and setup this equation:
{{{sqrt((x-(-2))^2+(y-y)^2)=sqrt((x-16)^2+(y-11)^2)}}}


Simplify that equation.
{{{sqrt((x+2)^2)=sqrt((x-16)^2+(y-11)^2)}}}

{{{(x+2)^2=(x-16)^2+(y-11)^2}}}

{{{x^2+4x+4=x^2-32x+256+y^2-22y+121}}}

{{{4x+4=-32x+256+y^2-22y+121}}}

{{{36x+4=y^2-22y+377}}}

{{{36x=y^2-22y+373}}}

{{{36x=y^2-22y+11^2+373-11^2}}}, completing the square because you wanted standard form

{{{36x=(y-11)^2+252}}}


{{{x=(1/36)(y-11)^2+252/36}}}


252/36=28/4=14/2=7


{{{highlight(x=(1/36)(y-11)^2+7)}}}