Anumber pattern is shown below. row 2: 8, 10. row 3: 15, 17, 19. row 4: 24, 26, 28, 30. row 5: 35, 37, 39, 41, 43. write an equation that can be used to find d, the difference between the last number and the first number, for any row r. show or explain your work.