tolong ya no 3, pls bantu pake cara

(4.5x)+(4.4x)+(4.3x)=144
20x+16x+12x=144
48x=144
x= 144:48= 3
p= 5x= 5.3=15cm
l = 4x=4.3 = 12cm
t = 3x=3.3 = 9cm
vol= 15x12x9= 1.620cm²