Question

find angle 3

measure of angle 1 = x
measure of angle 2 = x-6

Answer 1

is there anything else known about the angles?

Answer 2

m∠3 = 180 -(x + x - 6 )
= 180 - 2x + 6
= 186 - 2x.

Here is the steps to the problem:
First, we solve for x.

a=x
b=x-6
c= c

x+(x-6)+c=180
2x-6+c=180
+6 +6
2x+c=186
-c -c
2x =186-c
(2x)/2 = (186-c)/2
x = 93-c

a=93-c
b=87-c
c= c

(93-c)+(87-c)+c=180
-93 -87 -180
3=0
3c/=0/3
c=0
a=93
b=87
c=0