[tex]0.4(x - 3) + 2.5 = 0.5(4 + x) \\ 0.4x - 1.2 + 2.5 = 2 + 0.5x \\ 0.4x - 0.5x = 2 - 1.3 \\ - 0.1x = - 0.7 \\ 0.1x = 0.7 \\ x = 0.7 \div 0.1 \\ x = 7[/tex]