In a parallelogram opposite angles are congruent, that means:
Angle L = Angle N, replace L & N by they respective value, then
3x-25 = 2x-10 ==> x=15 , Now plug the value of x in any of the 2 sides
3(15) -25 =20°
hence Angle L =- Angle N = 20°
Now let's calculate Angle M. In a parallelogram the adjacent angle are supplementary, that means their sum = 180°, then
Angle N + Angle N = 180°==> Angle M = 180°-20° = 160°