In a quadrilateral ABCD, ∠A=90∘, ∠B=3x, ∠C=3x+5, ∠D=8x−15. Then, the value of ∠D is
65∘
60∘
20∘
145∘
Since the sum of interior angles of a quadrilateral is 360∘ 90+3x+3x+5+8x−15=36090+14x−10=36014x=360−80x=28014=20Then,∠D=8x−15 = 8(20)−15=145∘
The following figure shows a quadrilateral in which sides AB and DC are parallel. If ∠A:∠D=4:5, ∠B=(3x−15)o and ∠C=(4x+20)o, find each angle of the quadrilateral ABCD.
In a quadrilateral ABCD, ∠A = 90°, ∠B = 3x, ∠C = 3x + 5, ∠D = 8x - 15. Then, the value of ∠D is _____.