Answer: 60°
Explanation:
Looking at the figure, we know that the angles add up to 90°. We add both equations and solve for x.
3x+9+2x-4=90 [combine like terms]
5x+5=90 [subtract both sides by 5]
5x=85 [divide both sides by 5]
x=17
Now that we know x, we can plug it into ADB to find the angle.
3(17)+9 [multiply]
51+9 [add]
60
Now, we know that ADB is 60°.