Question

If Rick buys 50 tennis balls, he pays $30. If he buys only 40 tennis balls from the same store, he pays $20. Assuming that the pricing follows a linear model, what is the model?

y − 10 = 1(x − 10)

y − 50 = 1(x − 30)

y − 50 = 2(x − 30)

y − 20 = 2(x − 20)