Step-by-step explanation: tanΘ = opp/adj the opposite angle is 18 and the adjacent angle is 12, this is because the triangle is upside down thus, the 90 degrees is formed with the horizontal, and theta is the part of that 90 degrees made with the horizontal. Therefore, solve for the angle inside the triangle then subtract that from 90 and you have theta.
ANGLE BCD IS MADE UP OF 180 DEGREES ANGLE C IS 120 AND SINCE THE ENTIRE ANGLE IS 180 AND C AND D IS CONGRUENT AND 60 DEGREES IS LEFT WE DIVIDE BY 2 TO FIND OUR ANSWER OF 3O