In 2010, the percentage of private-sector workers who were in a union was 6.95%, and it decreased

Question:

In 2010, the percentage of private-sector workers who were in a union was 6.95%, and it decreased by about 0.25 percentage point per year until 2014.
a. Find an equation of a model to describe the situation. Explain what your variables represent.
b. Estimate when the percentage was 6.20%.
c. Estimate the percentage of private-sector workers who were not in a union in 2014.