Find the measure of angle A

55 degrees

Step-by-step explanation:

To find the measure of angle A, you first have to find x. To do that you use this equation: 80+(3+6x)+(7x+6)=180. You then simplify that equation.

80+(3+6x)+(7x+6)=180

80+3+6x+7x+6=180

89+13x=180

13x=180-89

13x=91

x=91/13

x=7

Then you plug x into the expression for angle A.

7x+6

7*(7)+6

49+6

55

Angle A=55 degrees

the answer is c: divide the arc's degree measure by 360°, then multiply by the circumference of the circle.