Question

7a+3b=85
a=2b
aflati nr nat a si b

Answer 1

Il inlocuiesti pe a cu 2b → 7*2b+3b= 85
14b+3b= 85→ 17b=85→ b=5 → a=2*5=10
* inseamna inmultire. Sper ca ti am fost de folos!!!!!!

Answer 2

$\displaystyle 7a+3b=85 \\ a=2b \\ 7a+3b=85 \Rightarrow 7 \cdot 2b+3b=85 \Rightarrow 14b+3b=85 \Rightarrow 17b=85 \Rightarrow \\ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\Rightarrow b= \frac{85}{17} \Rightarrow \boxed{b=5} \\ a=2b \Rightarrow a=2 \cdot 5 \Rightarrow \boxed{a=10}$