It seems that the y-intercept is 1, so you will be adding 1 to the equation. When you make a chart, you find that each number grows by 1 as well.
From this information, you will find that the answer is
y = x + 1
65:100 because there are 65 girls and then 65 girls + 35 boys = 100 total students
Well, if it is increasing at a fixed rate of 2 mm/s, then the volume would still be increasing at a rate of 2 mm/s when the diameter is 80 mm, if I understand your question correctly.
