0.3(n-n)=0.4-0.2(n-7)

Solution for 0.3(n-n)=0.4-0.2(n-7) equation:

Simplifying
0.3(n + -1n) = 0.4 + -0.2(n + -7)

Combine like terms: n + -1n = 0
0.3(0) = 0.4 + -0.2(n + -7)

Multiply 0.3 * 0
0.0 = 0.4 + -0.2(n + -7)

Anything times zero is zero.
0.0 = 0.4 + -0.2(n + -7)

Reorder the terms:
0.0 = 0.4 + -0.2(-7 + n)
0.0 = 0.4 + (-7 * -0.2 + n * -0.2)
0.0 = 0.4 + (1.4 + -0.2n)

Combine like terms: 0.4 + 1.4 = 1.8
0.0 = 1.8 + -0.2n

Solving
0.0 = 1.8 + -0.2n

Solving for variable 'n'.

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

Add '0.2n' to each side of the equation.
0.0 + 0.2n = 1.8 + -0.2n + 0.2n
Remove the zero:
0.2n = 1.8 + -0.2n + 0.2n

Combine like terms: -0.2n + 0.2n = 0.0
0.2n = 1.8 + 0.0
0.2n = 1.8

Divide each side by '0.2'.
n = 9

Simplifying
n = 9