Hello,
The first transform E1 is the homothetie of center (0,0) and ratio=2
The second transform E2 is the homothetie of center (0,0) and ratio=3/2
P=(3,k)
P'=E1(P)= E1((3,k))=(2*3,2*k)=(6,2k)
P''=E2(P')=E2(6,2k)=(3/2*6,3/2*2*k)=(9,3k)=(9,12)
==> 3k=12
k=4