I get too:
Sin 108/12.9 = sin 24/b
0.951056516.../12.9 = .406736643076/b
12.9/0.951056516 = b/.40673664307
12.9/0.951... = 13.563...
13.563 *.4067... = 5.516...
5.52 IS RIGHT!!!!! :)
12.9/sin 108 = b/sin24
sin 24 12.9/sin108 = b = 5.52 m
b / sin 24 = 12.9 / sin 108 multiply both sides by sin 24
b = 12.9 sin 24 / sin 108 ≈ 5.52 m
Sorry, EP....didn't see that you were answering this, as well