Question 982007
The description suggests a linear relationship.  This can define two data points as (x,y); x being the raw percentage score, y being the rescaled score.


These points are  (85,0) and (100,100).


Next objective is find the equation of the line which contains these two points.
{{{m=(100-0)/(100-85)=100/15=20/3}}}


Pick any or either point:
point-slope form line, {{{y-100=(20/3)(x-100)}}}
{{{y-100=20x/3-2000/3}}}
{{{y=(20/3)x+100-2000/3}}}
{{{y=(20/3)x+300/3-2000/3}}}
{{{highlight(y=(20/3)x-1700/3)}}}  or  {{{highlight(y=(20/3)x-566&2/3)}}}