Answer:
The y-coordinate of J'' is 8.
Step-by-step explanation:
The given rule of transformation is

It means, first the figure is reflected across the line y=x and then translated by the rule T(-3,-2).
From the given figure it is clear that the coordinates of point J are (10,-6).
If a figure is reflected across the line y=x, then

The coordinate of point J'.

If a figure is translate by the rule T(-3,-2), then

The coordinate of point J''.

Therefore the y-coordinate of J'' is 8.