I think for X you do:
[tex]180 = 90 + 2x + x[/tex]
then subtract the 90 to 180 and add the Xs together
[tex]90 = 3x[/tex]
then divide 90/3 to get X
[tex] \frac{90}{3} = 30[/tex]
to check put 30 in for X to make sure it = 180
Now for Y and Z I'm not sure what to do, I hope this helped a little