Răspuns :

pai faci cu regula de 3 simpla adica 20kg de lamai.......12 l suc
                                                      x kg..........................18 l suc
                                                             x este egal cu 20x18 supra 12
                                                                x este egal 30 de kg
20kgl.........12l
x..............18l

x=20*18/12
x=20*3/2
x=10*3
x=30kg