tolong bantuin ya soal mtk menentukan bangun yang sebangun pliss besok dikumpulin terima kasih

1. AD = a   
BC = b
QR = c

DC~PS
AD~RS
AB~QR
BC~QP

a : RS = DC : PS
a : 12 = 6 : 9
a = 12 x 6/9
a = 8 cm

b : QP = DC ; PS
b : 18 = 6 : 9
b = 18 x 6/9
b = 12 cm

AB : c = DC : PS
10 : c = 6 : 9
c = 10 x 9/6
c = 15 cm

2. a = 42 cm
b = 56 cm
x = ?
y = 48 cm

a~x
b~y

maka,
a : x = b : y
42 : x = 56 : 48
x = 42 x 48/56
x = 36 cm