lanjutin ya kak, dikit aja lho

y/5cm = 9/5
y = 9×5/5
y = 9
12/(12-x) = 9/5
9(12-x) = 5×12
108 - 9x = 60
108 - 60 = 9x
48 = 9x
x = 48/9 = 5,33