The number of young adult hikers in a country has steadily increased since 2010 the equation y=0.89x+9.78 can be used to estimate the number of young adults participating in hiking in the country ,in millions ,x years after 2010 a.) estimate the number of young adult hikers in the country in 2017 ? B.) in what year will 18.8 million young adults participate in hiking in the country ?