Answer:
The value of A is 20
Step-by-step explanation:
To find the answer, note that all triangles have a interior degree measurement of 180. Set the sum of the angles equal to 180.
71x - 1 + 20x + 90 = 180
91x + 89 = 180
91x = 91
x = 1
Now we can use this in the A angle to find the value.
A = 20x
A = 20(1)
A = 20
