<PRE><B>Question 1164788</B>
let x= years and y=height.  x is the independent variable and can be controlled, and y is dependent and depends on x.  This is standard throughout math and statistics.

ordered pairs (0, 3) and (4, 8)
point slope formula y-y1=m (x-x1) m slope (x1, y1) point
slope is 5/4
y-3=(5/4)(x)
y=(5/4)x+3
so after 15 years y=(5/4)*15+3
=21.75 feet.
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