Let the common ratio between a and b be x.
a = 2x, and b = 3x
XY is a straight line, rays OM and OP stand on it.
\\(\\begin{array}{l}{\ herefore \\angle \\mathrm{XOM}+\\angle \\mathrm{MOP}+\\angle \\mathrm{POY}=180^{\\circ}} \\\\ {b+a+\\angle \\mathrm{POY}=180^{\\circ}} \\\\ {3 x+2 x+90^{\\circ}=180^{\\circ}} \\\\ {5 x=90^{\\circ}} \\\\ {x=18^{\\circ}} \\\\ {a=2 x=2 \ imes 18=36^{\\circ}} \\\\ {b=3 x=3 \ imes 18=54^{\\circ}}\\end{array}\\)
MN is a straight line. Ray OX stands on it.
\\(\\begin{array}{l}{\ herefore b+c=180^{\\circ}(\ ext { Linear Pair })} \\\\ {54^{\\circ}+c=180^{\\circ}} \\\\ {c=180^{\\circ}-54^{\\circ}=126^{\\circ}} \\\\ {\ herefore c=126^{\\circ}}\\end{array}\\)