0.4(0.5k+3.5)-0.8=1.2

Solution for 0.4(0.5k+3.5)-0.8=1.2 equation:

Simplifying
0.4(0.5k + 3.5) + -0.8 = 1.2

Reorder the terms:
0.4(3.5 + 0.5k) + -0.8 = 1.2
(3.5 * 0.4 + 0.5k * 0.4) + -0.8 = 1.2
(1.4 + 0.2k) + -0.8 = 1.2

Reorder the terms:
1.4 + -0.8 + 0.2k = 1.2

Combine like terms: 1.4 + -0.8 = 0.6
0.6 + 0.2k = 1.2

Solving
0.6 + 0.2k = 1.2

Solving for variable 'k'.

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

Add '-0.6' to each side of the equation.
0.6 + -0.6 + 0.2k = 1.2 + -0.6

Combine like terms: 0.6 + -0.6 = 0.0
0.0 + 0.2k = 1.2 + -0.6
0.2k = 1.2 + -0.6

Combine like terms: 1.2 + -0.6 = 0.6
0.2k = 0.6

Divide each side by '0.2'.
k = 3

Simplifying
k = 3