Write down equations what you know.
NML is 28x-1, this is the total angle.
NME is 5x-1, this is the small part of the angle
EML is 115, this is the large part of the angle
So,
NME + EML should equal NML
5x-1 + 115 = 28x-1
Solve for x
Add 1 both sides
5x+115 = 28x
Subtract 5x both sides
115 = 23x
Divide 23 both sides
X=5