[tex]\sf \longmapsto45 - 4x = 75 - 6x[/tex]
[tex]\sf \longmapsto45 - 75 =- 6x + 4x[/tex]
[tex]\sf \longmapsto -30 =- 2x[/tex]
[tex] \sf \longmapsto \frac{ 30}{2} = x [/tex]
[tex]\sf \longmapsto 15 = x[/tex]
[tex]\sf \longmapsto \: x ≈15[/tex]
=> 45 - 4x = 75 - 6x
=> 45 - 75 = -6x + 4x
=> -30 = -2x
=> x = 30/2
=> x = 15
