Question

{x,y} directa proporționalitate {2,3}
2x-y=30

Answer 1

Xsupra 2 = y supra 3 = k rezulta 
2x3 supra 30 (30 cu 3 se simplifica) = 20 
2x-20=30
2x-10 =
x= 5

Answer 2

[tex]\it \{x, y\} d.p.\{2, 3\} \Rightarrow \dfrac{^{2)}x}{\ 2} = \dfrac{y}{3} \Rightarrow \dfrac{2x}{\ 4} = \dfrac{y}{3} =\dfrac{2x-y}{4-3} = 30 \\ \\ \\ \dfrac{2x}{4} =30 \Rightarrow 2x = 30\cdot4 \Rightarrow 2x = 120\Rightarrow x = 60 [/tex]

$\it \dfrac{y}{3} = 30 \Rightarrow y=30\cdot3 \Rightarrow y = 90$