Question

What is the distance between S and T? If necessary, round to the nearest tenth.

Answer 1

the two triangles are similar, so the sides are proportional
36/81=48/ST
ST=108

Answer 2

It would be 108 km. Since PR is parallel to RT, we have to divide 81/36 to get the scale factor, which in this case would be 2.25. Then you multiply 2.25 to 48, to get 108 km.