In a triangle RST, X lies on RS and Y lies on RT. XY is parallel to ST.
A sketch of the triangle will help. (right)
Assuming X is on side RS and Y is on RT,
we can place measurements as shown.
Notice that RXY and RST are similar triangles.
This means that the triangle RST is an enlargement of triangle RXY.
The scale factor is or
This means that RT is ×TY so RT = 6 × .
Length RT is 14.4 units.