Answer:
13.7 centimeters.
Explanation:
Please find the attachment.
We have been given that angle A of triangle ABC measures 42 degrees and angle C measures 50 degrees. The length of segment BC is 12 units. We are asked to find the length of segment AB.
We will use law of sines to solve for the length of AB as shown below:

Upon substituting our given values we will get,




Upon rounding our answer to the nearest tenth of a centimeter we will get,

Therefore, the length of AB s 13.7 centimeters.