The two angles together form a straight angle, i.e. an angle of 180 degrees. This means that
[tex] 7x + 2x+27 = 180 [/tex]
Sum like terms:
[tex] 9x+27 = 180 [/tex]
Subtract 27 from both sides:
[tex] 9x = 153 [/tex]
Divide both sides by 9:
[tex] x = \dfrac{153}{9} = 17 [/tex]
