Answer:
m∠ABD = 20°
Step-by-step explanation:
The bisector makes angles ABD and BDC congruent, so ...
7x -1 = 4x +8
3x = 9 . . . . . . add 1-4x to both sides
x = 3
m∠ABD = (7x-1)° = (7·3 -1)°
they are the same because its a rigid transformation; rigid means the shape and size doesn't change.
width is 5, length is 8