4=0.4(3d-f)

Solution for 4=0.4(3d-f) equation:

Simplifying
4 = 0.4(3d + -1f)
4 = (3d * 0.4 + -1f * 0.4)
4 = (1.2d + -0.4f)

Solving
4 = 1.2d + -0.4f

Solving for variable 'd'.

Move all terms containing d to the left, all other terms to the right.

Add '-1.2d' to each side of the equation.
4 + -1.2d = 1.2d + -1.2d + -0.4f

Combine like terms: 1.2d + -1.2d = 0.0
4 + -1.2d = 0.0 + -0.4f
4 + -1.2d = -0.4f

Add '-4' to each side of the equation.
4 + -4 + -1.2d = -4 + -0.4f

Combine like terms: 4 + -4 = 0
0 + -1.2d = -4 + -0.4f
-1.2d = -4 + -0.4f

Divide each side by '-1.2'.
d = 3.333333333 + 0.3333333333f

Simplifying
d = 3.333333333 + 0.3333333333f