Answer :
Sometimes the editor can make life a little frustrating. There are parts I can't read easily, but here's how you do the problem.
The largest angle is going to be opposite the longest line.
c^2 = b^2 + a^2 - 2 *a * b * Cos C
c = 12
b = 11
a = 6
C = ???
12^2 = 11^2 + 6^2 - 2*11*6 * Cos C
144 = 121 + 36 - 132 * Cos C
144 = 157 - 132 * Cos C
144 - 157 = -132 * Cos C
-13 = -132 Cos C
-13/-132 = Cos C
0.09848 = Cos C
Cos-1(0.09848) = C
84.348 degrees
The largest angle is going to be opposite the longest line.
c^2 = b^2 + a^2 - 2 *a * b * Cos C
c = 12
b = 11
a = 6
C = ???
12^2 = 11^2 + 6^2 - 2*11*6 * Cos C
144 = 121 + 36 - 132 * Cos C
144 = 157 - 132 * Cos C
144 - 157 = -132 * Cos C
-13 = -132 Cos C
-13/-132 = Cos C
0.09848 = Cos C
Cos-1(0.09848) = C
84.348 degrees