Question

o cutie de zece becuri cantareste 78 g. cutia goala cantareste cat 3 becuri. cat cantaresc becurile?

Answer 1

$c \to cat \ cantareste \ cutia \\ b \to cat \ cantareste \ un \ bec \\\\\\ c+10b=78 \\\\ \underline{c=3b} \\\\\\ 3b+10b=78 \\\\ 13b=78 \ \ \ |:13 \\\\ \boxed{b=6g - cantareste \ un \ bec} \\\\ c=3*6 \\\\ \boxed{c=18g -cantareste \ cutia} \\\\\\ \hbox{Cele 10 becuri cantaresc:} \\ 78g-18g \longrightarrow \underline{60g}$