How to find a point along a straight line

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C#

WPF

I have two points (x1, y1) and (x2,y2) and have a straight line between the 2 points. From the distance of the line I have to decrease some length (Percentage of the original length). How do I get the point where the new length is to draw a path between (x1,y1) & (x3,y3)

So far I have this and developed in WPF C#:

private void DrawPath(Point origination, Point destination, float decreasePct)
        {
            Canvas.Children.Clear();
            var distance = GetLineLength(origination, destination);
            
            var path = new PathFigure();

            path.StartPoint = origination;

            path.Segments.Add(new LineSegment(destination, true));

            // Create a PathGeometry to contain the figure.
            var pathGeometry = new PathGeometry();
            pathGeometry.Figures.Add(path);

            // Display the PathGeometry.
            var myPath = new Path {Stroke = Brushes.Black, StrokeThickness = 6, Data = pathGeometry};

            Canvas.Children.Add(myPath);
        }

private int GetLineLength(Point origination, Point destination)
        {
            var x = destination.X - origination.X;
            var y = destination.Y - origination.Y;

            var pyth = Math.Pow(x, 2) + Math.Pow(y, 2);

            return (int)Math.Sqrt(pyth);
        }

Any help would be appreciated!!!