Answer:
Explanation:
Angle ABD plus angle DBC = 90. That's what that little square in the corner there means...a right angle which is 90 degrees. Using substitution,
3x + 15 + 2x = 90 and
5x + 15 = 90 and
5x = 75 so
x = 15. Now we need to plug in 15 for x in 2x to get 2(15) which is 30. Second choice down.