Imi puteti explica?​

[tex]a = \dfrac{b}{3}\cdot 5+7\Big|\cdot 3\Rightarrow 3a = 5b+21 \Rightarrow 5b = 3a-21\\ \\ 2a+b = 170\Big|\cdot 5 \Rightarrow 10a+5b = 850 \Rightarrow 10a+(3a-21) = 850 \Rightarrow \\ \\ \Rightarrow 13a = 850+21 \Rightarrow 13a = 871 \Rightarrow a = \dfrac{871}{13} \Rightarrow \boxed{a = 67} \\ \\ 5b = 3\cdot 67-21 \Rightarrow 5b = 180 \Rightarrow b = \dfrac{180}{5}\Rightarrow \boxed{b = 36 }[/tex]

Răspuns:  a = 67   si  b = 36

Explicație pas cu pas:

a : (b/3) = 5 rest 7 ⇒  a = 5 × (b/3) + 7

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2 × a + b = 170

2 × ( 5 b/3 + 7) + b = 170   l  × 3

10 b + 3 b = 3 × (170 - 14)

13 b = 3 × 156  l : 13 ⇒   b = 36

a = 5 × 36/3 + 7       ⇒   a = 67