step 1
Find out the slope WX
W(2,-3) and X(-4,9)
m=(9+3)/(-4-2)
m=12/-6
m=-2
step 2
Find out the slope YZ
Y(5,y) and Z(-1,1)
m=(1-y)/(-1-5)
m=(1-y)/-6
m=(y-1)/6
step 3
Remember that
If two lines are perpendicular
then
their slopes are negative reciprocal
that means
(y-1)/6=1/2 -----> because the negative reciprocal of -2 is 1/2
solve for y
2y-2=6
2y=6+2
2y=8
y=4