Final answer:
Similar triangles can be determined using the Angle-Angle criterion and side proportions, but the specific triangles and relationships in the current context are unclear.
Step-by-step explanation:
To determine whether triangles are similar, one must examine the congruence of angles and the proportionality of sides. From the provided information, we see references to triangles being similar and proportions being used to solve for an unknown variable x. Applying knowledge of similarity and congruence in triangles, as well as using trigonometry to establish relationships between the sides and angles of triangles, one can often establish similarity and find the missing variables.
Resolving the issue of which triangles are similar and what expression to use to solve for x would typically involve using these relationships. However, from the provided information, it is not clear what the specific triangles or the given sides and angles are. Usually, the Angle-Angle (AA) criterion, where two triangles have two corresponding angles equal, is a common way to determine similarity. From there, similarity can be used to establish proportional relationships between corresponding sides of the triangles to solve for x.