Answer:
20
Step-by-step explanation:
we know that
In a parallelogram, opposite angles are congruent and consecutive angles are supplementary
In this problem
M and N are consecutive angles so
[tex]m\angle M+m\angle N=180^o[/tex]
substitute the given values
[tex]3x^o+(8x-40)^o=180^o[/tex]
solve for x
[tex]11x-40=180\\11x=220\\x=20[/tex]
