50 points!!! please hurry i need this answer . see pic below

Sum of two Interiors=Exterior
[tex]\\ \rm\rightarrowtail x+20+3x-7=7x-17[/tex]
[tex]\\ \rm\rightarrowtail 4x+13=7x-17[/tex]
[tex]\\ \rm\rightarrowtail -3x=-30[/tex]
[tex]\\ \rm\rightarrowtail x=10[/tex]
m<NOP=7(10)-17=70-17=53