Calculate Unknown Points Based Off A Known Point And The Percentage Of Two Prior Points

There are an infinite number of point A & B numbers that will satisfy the point C formula

e.g. given a point C value of 100 points A & B could be

361,8123 & -61.832197
261.8123 & -.0198999
161.8123 & 61.6924

Please explain with examples exactly what results you expect

This looks like it will end up being some kind of "solve a system of equations" problem like you learned back in high school. I would suggest that you start by reviewing your algebra: http://www.purplemath.com/modules/systlin1.htm

There are some inconsistencies in your problem statement. You mention trying to find B1, but there is no B1 in your equations (did you mean B2?). It is also unclear to me whether D1 and E1 will also be known.

If I assume that either D1 or E1 are known, and that B2 and B1 are the same thing, then you should have a relatively simple system of 2 linear equations in 2 unkowns. The strategies in the algebra tutorial should be useful in solving such a system.

Standard rule of thumb when solving systems of equations is that you need at least as many equations as you have unknowns in order to find a unique solution. In the scenario you describe, you have 3 equations, and potentially 4 unknowns. When you have 4 unknowns, then you will have a scenario like Richard described above -- you can only find a relationship between A1 and B2. You will usually not be able to find a single, unique solution for A1 and B2.