Two words. The input and the output determine this
If 2-4=20 than x is equal to 12
2+2x= 19+2x
<u> -2x= -2x</u> (they both cross out)
2= 19
there is no solution for x
So in a triangle ; angle sum is 180°
so 3x-16 + x+6 + x =180
5x -10 =180
x= 190/5
x= 38
so M angle is 3x-16 = 3×38 -16 =114-16 = 98°
your answer is 98°