the formula for slope is:
m= (y₂-y₁)/(x₂-x₁)
we can assume that mass represents x and volume represents y
so we can pick any 2 x and y pairs to begin.
i will chose the first 2
(12.2, 5.9) and (33.2, 16.1)
now we can plug in out numbers into the equation
m= (16.1 - 5.9) / (33.2 - 12.2)
m= 10.2/21
so the slope is 10.2/21 or 0.485714...
the nearest whole number would be 1
hope this helps