First of all, using the information about constant rate we can say that these points are located on a straight line. Indeed, the logic is about a constant rate. Then, we can easily claim that the points are located on a quasi-linear function, y=kx+b. We could solve this problem by setting up a system of equations. The system is this:
[tex]\left \{ {{19=14k+b} \atop {22=20k+b}} \right. \\[/tex]
By solving it, we find that k=0.5 and b=12. Then the function is y=0.5x+12
We have to find that how many rows were completed, before Elene started, i.e, x = 0. Then y=0.5*0+12 = 12. The answer is 12 rows.
