KLP and PLM form a linear pair, so:
KLP+PLM=180
3x+PLM=180
PLM=180−3x
Same with PMN and PML, so:
PMN+PML=180
(2x+72)+PML=180
PML=108−2x
Since PLM, PML, and LPM are the angles of the same triangle, their sums must be equal to 180. So:
PML+PLM+LPM=180
(108−2x)+(180−3x)+(x)=180
288−4x=180
−4x=−108
x=27