I will not do this for you, but I will tell you how to do it.
First you need the distance from point A to point B.
Then you need the equation of the line through A and B.
Point T will fall on the line through A and B and the distance from A to T will be 2/7 of the distance from A to B.
Set up an equation using the distance formula and the unknown co-ordinates of T and solve for x.