geometry

 

In the triangle on the left, you have a 90^o right angle and a 48^o angle  

 

The total of the interior angles of a triange is 180^o so the third angle is 42^o  

 

Across from the 42^o angle is its vertical angle which is equal so it's also 42^o  

 

So the two angles we know in the triangle on the right total (42^o + 66^o) = 108^o   

 

That means angle M is (180^o – 108^o)  =  72^o   

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