I'm not sure I understand your question, but I'll give it a shot.
With the equation y = 4.81x + 17.4, when $x = 15, y = 72.15 + 17.4, which equals 89.55. This rounds to [90].
When x = 9, y = 43.29 + 17.4, which equals 60.68. This rounds to [61].
You are welcome.
