The 2-point form of the equation for a line is useful when you are given two points to work with:
y = (y2 -y1)/(x2 -x1)(x -x1) +y1
The independent variable (x) is apparently "algae blooms" and is to be represented by "a". The dependent variable (y) is "number of fish" and is to be represented by "f". So, we have ...
f = (4 -10)/(25 -10)(a -10) +10
f = -6/15(a -10) +10
f = -2/5a +14 . . . an equation for the scenario
Four a=4, the fish population is predicted to be ...
f = -2/5(4) +14 = 12.4
There will be about 12 fish when there are 4 algae blooms.
