X+Z = 180
Y+60-X = 180......(1)
X+Z = Y+60-X
2X+Z-Y = 60
Also, given X = 3Y-3Z
6Y-6Z+Z-Y = 60
Y-Z = 12
Y = 12+Z...........(2)
(2) IN (1) 72+Z-X = 180
Z-X = 108
X+Z = 180
2Z = 288
Z = 144, Then X = 36

C is the answer.
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Obs.: all angles are measured in degrees.



\(x = 3\left( {y - z} \right)\,\,\,\,\,\left( * \right)\)

\(? = x\)

\(\left( {{\rm{Last}}\,\,{\rm{figure}}} \right)\,\,\,\,x + z\,\, = \,\,\left[ {180} \right]\,\, = \,\,\left( {60 - x} \right) + y\,\,\,\,\, \Rightarrow \,\,\,\,\,2x = y - z + 60\,\,\,\,\mathop = \limits^{\left( * \right)} \,\,\,\,{x \over 3} + 60\)

\(2x - {x \over 3} = 60\,\,\,\,\mathop \Rightarrow \limits^{ \cdot {\mkern 1mu} 3} \,\,\,\,6x - x = 3 \cdot 60\,\,\,\, \Rightarrow \,\,\,\,? = {{3 \cdot 6 \cdot 10} \over 5} = 36\)


The correct answer is (C).


We follow the notations and rationale taught in the GMATH method.

Regards,
Fabio.
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