Final answer:
Without additional context on how angles 5, 7, and 8 are related, it is not possible to determine the measure of angle 7 with the information provided.
Step-by-step explanation:
To find m∠7, we need more context about the relationship between the angles. The provided equations for angles 5 and 8 don't give us enough information to determine the measure of angle 7 without additional relationships or figures. As the relationship between these angles isn't specified, and the reference information provided seems to be unrelated to the question about geometric angles, it is not possible to give a factual answer. The reference information seems to pertain to physics and trigonometry problems involving vectors and scattering angles which are not directly related to finding m∠7 in geometrical terms.