Answer:
AC=6.37
Explanation:
First you need to find m∠C
A triangle = 180 so you need to add 108 and 31
subtract 180-139
you get 41, so m∠C=41
Now we know all the angle measures.
Next we will use the law of sines
Go to google and type "law of sines calc"
google can usually provide with the formula and will even do the equation for you if you type in the numbers
So all you do is plug in the numbers and google will give you 6.37