1. The problem is to find a certain value or relationship using 2 triangles. 2. When using two triangles, common methods include comparing corresponding sides or angles, using similarity or congruence criteria. 3. Important rules: - Triangles are similar if their corresponding angles are equal and sides are proportional. - Triangles are congruent if all corresponding sides and angles are equal. 4. To solve, identify the two triangles and determine if they are similar or congruent. 5. Use the properties of similarity or congruence to set up equations relating sides or angles. 6. Solve these equations step-by-step to find the unknown value. 7. For example, if triangles are similar, use the ratio of corresponding sides: $$\frac{a}{a'} = \frac{b}{b'} = \frac{c}{c'}$$ 8. Substitute known values and solve for the unknown. 9. If triangles are congruent, corresponding sides and angles are equal, so set them equal directly. 10. Always check your solution by verifying the triangle properties hold.