The formula h - 15 = 3.2t gives the height "h" in inches of a plant after "t" weeks of planting. What is the rate at which the plant's height is increasing?

A 3.2 inches per week.

explanation

h =15 + 3.2t gives the height of a shrub in inches after t weeks. When planting occurs the height is 15 + 3.2 × 0 = 15 inches . After one week the height is 15 + 3.2 = 18.2 inches . The rate at which the height increases is 18.2 - 15 = 3.2 inches