Malem,,tolong yg bisa dijawab

3. y = 30-20=10cm
12/x = 20/30
x= 12.30 /20 = 18 cm
4. 2/5 (2a) = a-3
4a = 5(a-3)
4a = 5a-15
15 = 5a-4a
15=a
5. 48/(48-6) = 56/(56-3-x)
48/42 = 56/(53-x)
53-x = 42.56/48
53-x = 49
x = 53-49=4 cm