Answer:
<A = 75degrees
Step-by-step explanation:
From the triangle given;
arcDA + arc AD + arcBD = 360 degrees
131 + 79 + arcBD = 360
210 + arcBD = 360
arcBD = 360 -210
arcBD = 150 degrees
Since the angle at the vertex <A is half that at the arc BD, hence;
<A = 1/2 arcBD
<A = 1/2 * 150
<A = 75degrees
Hence the measure of angle A s 75degrees
