Answer:
84°
Step-by-step explanation:
[tex]\because (13n - 16) \degree + (7n + 12) \degree + (6n)\degree \\= 360\degree \\ \\ \therefore \: (26n - 4) \degree= 360\degree \\ \\ \therefore \: 26n - 4= 360 \\ \\ \therefore \: 26n = 360 + 4 \\ \\ \therefore \: 26n = 364 \\ \\ \therefore \: n = \frac{364}{26} \\ \\ \therefore \: n = 14 \\ \\\because m\overset { \frown}{BC} = (6n)°\\ \\\therefore \:m \overset { \frown}{BC} =(6\times 14)° \\ \\ \huge \purple {\boxed {\therefore \:m\overset { \frown}{BC}= 84°}} \\ [/tex]
