17)regula de 3 simpla
4 l -----24 lei
6 l -----x lei
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x =6*24 /4 =36 lei
18) 140 : 2 =70 grade
19)a+b+c =180 grade
a =2b ; b =a/2 ; a =2c /2
b =c /2 inlocuim pe a si b in prima relatie
2c /2 +c /2 +c =180 numitor comun 2
2c +c +2c =360
5c =360
c =72 grade
b =c /2
b =72/2
b =36 gr.
a =2b
a =2*36
a =72 gr
72+36+72 =180 gr.