Vectors starting at different origins

[dw85745]

I'm trying to determine the projected value for a new vector based on 3 vectors starting at different origins. This is in a 2D plane not 3D. Hope someone can help with a formula.

For example:

Vector 1: (100, 100) - (300, 300)
Vector 2: (100, 150) - (300, 300)
Vector 3: (100, 175) - (300, 300)

So the y value for the composite vector end point at say point (301, yyyy) would be???


Thanks
David