Why does there seem to be so much error in the laws of sines and cosines?

OK, I did the Law of Cosines 3 times and came up with 60.647 , 20.404 and 98.949 respectively for angles A, B and C. Remember, the Law of Cosines does not have an ambiguous case, unlike the Law of Sines. I suspect (without further investigating) that his may be the culprit. My advice: Always use the Law of Cosines whenever you can. In this case, when all sides are known, clearly a case for Law of Cosines

Switching from Law of Cosines to Law of Sines may introduce the ambiguous case and create extraneous solutions, so it is better to stick with Law of Cosines as much as possible. If you do change to Law of Sines, you can test your results by substituting ALL of your sides and angles into the proportion. If you do not obtain equivalent results, you have the extraneous solution and will need to rework the problem using the supplement of the angle you initially obtained. The link connects to Google Slides I prepared for my students. Testing solutions using Law of Sines