Answer:
27°
Step-by-step explanation:
when you see a square to represent that angle, that means that angle is 90 degrees (a right angle)
the angle of a straight line is 180
so [tex]180-90=90[/tex]
[tex]3x+9=90[/tex]
[tex]3x=81[/tex]
[tex]x=27[/tex]
