We know: the sum of measures of triangle angles is 180°.
Therefore we have the equation
[tex]m\angle1+m\angle2+m\angle3=180^o\to m\angle1=180^o-m\angle2-m\angle3[/tex]
Substitute [tex]m\angle2=2x,\ m\angle3=5x[/tex]:
[tex]m\angle1=180-2x-5x=180-7x[/tex]
Answer: 180 - 7x
