The explanation depends on the so-called Side-splitter Theorem from plane geometry.
If you draw a line segment and make it the hypotenuse of a right triangle, then draw lines parallel to the legs of the right triangle, the Side-splitter Theorem will show you how to get the answer below.
If the co-ordinates of the ends of the line segment are A(a,b) and C(c,d) and you want a point 100p% of the way from A to C, the co-ordinates are
abscissa: p*c+(1-p)a
ordinate: p*d+(1-p)b
In your case p=.6 (3/5) and 1-p=.4(2/5).
You got the whole lesson.
I hope it helps.
Robert U.
what is this in fraction form x,y09/01/21