Answer: 55 degrees
==========================================================
Reason:
For any triangle, the inside angles always add to 180 degrees.
(angle1)+(angle2)+(angle3) = 180
(6x+13)+(79)+(6x+4) = 180
(6x+6x)+(13+79+4) = 180
12x+96 = 180
12x = 180-96
12x = 84
x = 84/12
x = 7
Then use this to compute angle A.
A = 6x+13 = 6*7+13 = 42+13 = 55 degrees
If you wanted, you can compute the other angle as well
6x+4 = 6*7+4 = 42+4 = 46 degrees
Then as a check:
(angle1)+(angle2)+(angle3) = (55)+(79)+(46) = 180
which confirms the answer.
