When Lou started his current job, his employer told him that he would receive two vacation days for each full year he worked. Let x represent the number of years he has worked for the company and y...

When Lou started his current job, his employer told him that he would receive two vacation days for each full year he worked. Let x represent the number of years he has worked for the company and y represent the number of paid vacation days he earned.

a. Write an equation that models the relationship between these two variables.

b. How long will it take him to earn 18 paid vacation days?