Final answer:
Choosing an equation to find angle GFE requires understanding of geometric context, such as supplementary angles, but cannot be definitively answered without more information or a visible diagram. Correct option is option number d.
Step-by-step explanation:
The equation that can be used to find the measure of angle GFE can be derived from the concept of supplementary angles, which states that two angles are supplementary if their sum is 180 degrees.
In order to provide a definite answer, we would need to know more about the specific geometric context in which angle GFE is situated. For example, if angles GFE and FEG are adjacent and form a straight line, then we can confirm option (a) is correct: ∠GFE = 180 - ∠FEG, because they would be supplementary angles. Without additional context or a diagram, we cannot determine which of the given options is correct.