We will find the length of the longest side as follows:
*First: We can see that the other angle that is missing is 60°. Now, using the law of sines we find the other side of the triangle [Not the longest yet], that is:
From this we solve for y:
*Second: Now that we have the measure of the other side of the triangle (6sqrt3, approximately 10.4 inches) we find the measure of the largest side:
So, the length of the longest side is 12sqrt(3) inches (Approximately 20.8 inches).