The population of Center City is modeled by exponential function f, where x is the number of years after the year 2015. The graph of f is shown on the grid.

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For a party, you can spend no more than $ 20 on cakes. The egg cake cost is $ 4 and the cream cake cost is $ 2. Write the linear inequality that models the situation. Graph the inequality. Suppose that the number of egg cakes we buy is represented by x and the number of cream cakes we buy is represented by y.