[tex] \huge \frac{a}{3} = \frac{b}{5} = \frac{c}{7} = k[/tex]
[tex] \\ \\ \\ \huge \frac{a}{3} = k \rightarrow \: a = 3k \\ \\ \\ \\ \huge \frac{b}{5} = k \rightarrow \: b= 5k \\ \\ \\ \\ \huge \frac{c}{7} = k \rightarrow \: c = 7k[/tex]
[tex] \\ \\ \\ \\ \huge \: a + b + c = 60 \\ \\ \huge \: 3k + 5k + 7k = 60 \\ \\ \huge \: 15k = 60 \\ \\ \huge \: k = 60 \div 15 \\ \\ \huge \underline{k = 4}[/tex]
[tex] \\ \\ \\ \\ \\ \\ \huge \: a = 3k \\ \huge k = 4 \rightarrow \: a = 3 \times 4 \rightarrow \: \\ \\ \huge \rightarrow\pink{\boxed{ a= 12}}[/tex]
[tex]\\ \\ \\ \huge \: b = 5k \\ \huge k = 4 \rightarrow \: b = 5\times 4 \rightarrow \: \\ \\ \huge \rightarrow\pink{\boxed{ b= 20}}[/tex]
[tex] \\ \\ \\ \huge \: c= 7k \\ \huge k = 4 \rightarrow \: c = 7 \times 4 \rightarrow \: \\\ \\ \huge \rightarrow\pink{\boxed{ c= 28}}\\ \\ \\[/tex]
PROBA:
[tex] a + b + c =60 \\ 12 + 20 + 28 = 60 \\ 60 = 60 \blue{ \: \: \: \: \: \: \: \: Adevărat}[/tex]
