We just distribute the numbers out inside the parenthesis:
0.4(
2x +

) = 3[0.2x + (-2)] - 4
(0.4 × 2x) + (0.4 ×

) = (3 × 0.2x) + (3 × -2) - 4
0.8x + 0.2 = 0.6x - 6 - 4
Join the like terms:
0.8x + 0.2 = 0.6x - 10
0.8x - 0.6x = -10 - 0.2
0.2x = -10.2
Divide by 0.2 to isolate x

=

0.2 and 0.2 cancels out
x = -51