Which relationship is always true for the angles r, x, y, and z of triangle abc? x + z = y 180 degrees − x = r x + y + z = 180 degrees x + y + z = 90 degrees i don't think its c. because there is an exterior angle. i think it would be b.

That's the second one,

180 - x = r

Whenever two lines cross we get congruent opposite angles and supplemental adjacent angles, i.e. they add to 180 degrees.

The first one is almost right; we have r+y+z=180 and r+x=180 so x=y+z not quite what was written.

your question is incomplete, write all the numbers in the sequence that it tells you.  

step-by-step explanation: