You have the following points for the vertices of a triangle:
R(18,2)
S(12,15)
T(3,9)
If the triangle is dilated with a factor 2/3 with the origin as reference, you simpliy add to each coordinate of each point the result of the product of the coordinate by the scale factor. You proceed as follow for each vertex:
R(18,2)
18 + 18(2/3) = 30
2 + 2(2/3) = 10/3
Then:
R'(30 , 10/3) "this is the dilated point for R"
S(12 ,15)
12 + 12(2/3) = 20
15 + 15(2/3) = 25
S'(20 , 25)
T(3,9)
3 + 3(2/3) = 5
9 + 9(2/3) = 15
T'(5 , 15)