Answer:
 .
.
Step-by-step explanation:
A line that goes through  and
 and  where
 where  would have a slope of
 would have a slope of  .
.
The slope of the line that goes through  and
 and  would thus be:
 would thus be:
 .
.
Two lines in a cartesian plane are perpendicular to one another if and only if the product of their slopes is  .
. 
Thus, if  and
 and  denote the slope of the first and second lines in this question,
 denote the slope of the first and second lines in this question,  since the two lines are perpendicular to one another. Since
 since the two lines are perpendicular to one another. Since  , the slope of the first line would be:
, the slope of the first line would be:
 .
.
Given that the first line goes through the point  , the point-slope equation of that line would be:
, the point-slope equation of that line would be:
 .
.
 .
.
Substitute in  to find the
 to find the  -coordinate of the point in question:
-coordinate of the point in question:
 .
.