∡IAD and ∡GCJ are alternate exterior angles, and therefore equal.
that means ∡IAD is 70°, now, ∡DAK is a right-angle, and "x" is there, and ∡x + ∡IAD add up to 90°, and therefore are supplementary angles.
we know ∡IAD is 70°, therefore then
x + 70 = 90
x = 90 - 70.