For the general case, the n-gon, you got

degrees. The 13-gon thus has 1980 degrees in total.
Distribute the two to each of the values in the parentheses.
-4 +6a-10= 1-1a
Then move like terms to the same side to simplify.
6a+1a=1+10+4
7a=15
a=15/7
Answer:
35
Step-by-step explanation:
10 + 25 = 35
Looks like it's already in slope-intercept form.
slope-intercept form: y = mx + b
in this case, m is 8 and b is 4