At the beginning of the year, Serenity had $90 in savings and saved an additional $13 each week thereafter. Andrew started the year with $40 and saved $18 every week. Let SS represent the amount of money Serenity has saved tt weeks after the beginning of the year and let AA represent the amount of money Andrew has saved tt weeks after the beginning of the year. Write an equation for each situation, in terms of t, t, and determine the number of weeks after the beginning of the year until Serenity and Andrew have the same amount of money saved.