Rhombus Angle Calculation: Finding Angle A When B = 80 Degrees

According to the properties of a quadrilateral, each pair of opposite angles are equal to each other.

Therefore:

$B=C=80$

$A=D$

Additionally, we know that the sum of the angles in a quadrilateral equals 360 degrees.

Therefore, we can calculate angles A and D as follows:

$360-80-80=200$

$200:2=100$

Angle A is equal to 100.