According to a Pew Research survey, the percentage of Americans aged 12 and older who had listened to online radio in the previous month increased from 27% in 2010 to 64% in 2018. During this same period, the percentage of U.S. cellphone users who had ever listened to online radio in a car, using a phone, increased from 6% to 44%. Both of these trends changed at a roughly linear rate. Source: Pew Research Center.
(a) Find a linear equation expressing the percentage of Americans aged 12 and older, y_o, who had listened to online radio in the previous month in terms of t, the number of years since 2000.
(b) Find a linear equation expressing the percentage of U.S. cellphone users, y_c, who had ever listened to online radio in a car using a phone in terms of t, the number of years since 2000.
(c) Find the rate of change over time for the percentage in each group.