Step-by-step explanation: All 3 angles in any triangle add up to 180, in the first triangle (one on the left), you have 58 and 78 degrees, add them both and subtract from 180, you get 44 degrees for angle C on the left. Do the same on the right side of the triangle, you should get 35 degrees for angle C on the right. Add them both up, (35+44) then subtract from 180 degrees to find the measure of angle BCD.
