Salut !

[tex]3x+5(2x-1)=21\\\Leftrightarrow 3x+10x-5=21\\\Leftrightarrow 13x=26\\ \Leftrightarrow x=2\\S=\{2\}[/tex]

Bonjour,

3x + 5(2x - 1) = 21

3x + 10x - 5 = 21

13x - 5 = 21

13x = 26

x = 26/13

x = 2