You need the Law of Sines for this. In our case we have the measure of angle B and side b, we have the measure of angle A and are looking for side a, or x. Setting up the Law using our info, we have [tex] \frac{x}{sin(42)} = \frac{9}{sin(29)} [/tex]. We will solve for x by multiplying both sides by sin(42): [tex]x= \frac{9sin(42)}{sin(29)} [/tex], first choice above.
