Law of Cosines? [20 characters]?

So were learning the Law of Sines/ Law of Cosines in math and I am totally lost. Sines i'm alright with, but it's that law of cosines that is really stumping me. Can anyone walk me through this problem so I know how to do the rest. Thank you so, so much! I have to solve for x; angle A = x angle B =... show more So were learning the Law of Sines/ Law of Cosines in math and I am totally lost. Sines i'm alright with, but it's that law of cosines that is really stumping me. Can anyone walk me through this problem so I know how to do the rest. Thank you so, so much!

I have to solve for x;

angle A = x
angle B = unknown
angle C = unknown

side a = 345
side b = 648
side c = 442

Thank you :)
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