7x1,000,000,000-5.8x1,000,000,000

1200000000

Step-by-step explanation:

<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