Explicație pas cu pas:
[tex](x) + (7x) + (4x) = 7x + 4 \\ 12x = 7x + 4 \\ 12x - 7x = 4 \\ 5x = 4 \\ x = \frac{4}{5} \\ x = 0.8 \\..................................... \\ 0.8 + (7 \times 0.8) + (4 \times 0.8) = 7 \times 0.8 + 4 = \\ 0.8 + 5.6 + 3.2 = 5.6 + 4 \\ 9.6 = 9.6[/tex]