Hello, Guest!~
I'm going to elaborate on Electric Pavlov's excellent answer.
So, basically, the Law of Sines says that, according to Khanacademy, a side labeled, "A" over the sine * opposite of it, which is, angle "a", is equal to a side labeled, "B", over the sine * opposite of that side, which is the angle "b".
In short, you end up with, Side AAngle a=Side BAngle b, and you can add the third side the same way: Side AAngle a=Side BAngle b=Side CAngle c
For your case, we get:
sin(70)5.7=x5sin(x)∗5.7=sin(70)∗5sin(x)=5sin(70)5.7x=sin−1(5sin(70)5.7)
I do hope the math is correct.
From here, you can just plug it in!
I hope you did take away something from my answer!
-TheLovely1