Hi there!
(z)
We know that the two segments with "z" are congruent, so:
z + 15 = 5z + 9
Solve for z:
15 = 4z + 9
6 = 4z
z = 3/2
(y)
We know that (7y + 6) = 90° (indicated by the square angle), so:
7y + 6 = 90
7y = 84
y = 12°
(x)
Segments (x + 26) and (3x - 8) are congruent, so:
x + 26 = 3x - 8
26 = 2x - 8
34 = 2x
x = 17