So I answered your other question, here we use another law, specifically the law of sins.
Law is sins is
SinA/a = SinB/b = SinC/c
Since you are given A’s side and length we can use this to be the “base” of the problem and solve for C because we are also given this angle.
It’s set up like this:
Sin42/12 = Sin56/C
Cross multiply
12sin56 = Csin42
Divide by Sin42 to get C by itself
(12sin56)/(Sin42) = C
The answer you should get is 14.86 which rounded is 14.9
D is your answer.
Hope it helps lmk if there are questions