Please help [photo] I’ve been stuck on this

What is the common difference in the following arithmetic sequence? 7,3,-1,-5

Aresearch company wants to test the claim that a new multivitamin to improve short term memory. state the objective of the experiment, suggest a population, determine the experimental and control groups, and describe a sample procedure.

What is the location of point g, which partitions the directed line segment from d to f into a 5: 4 ratio? –1 0 2 3