400=X+(X*0.8)

Solution for 400=X+(X*0.8) equation:

Simplifying
400 = X + (X * 0.8)

Reorder the terms for easier multiplication:
400 = X + (0.8X)

Combine like terms: X + (0.8X) = 1.8X
400 = 1.8X

Solving
400 = 1.8X

Solving for variable 'X'.

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

Add '-1.8X' to each side of the equation.
400 + -1.8X = 1.8X + -1.8X

Combine like terms: 1.8X + -1.8X = 0.0
400 + -1.8X = 0.0

Add '-400' to each side of the equation.
400 + -400 + -1.8X = 0.0 + -400

Combine like terms: 400 + -400 = 0
0 + -1.8X = 0.0 + -400
-1.8X = 0.0 + -400

Combine like terms: 0.0 + -400 = -400
-1.8X = -400

Divide each side by '-1.8'.
X = 222.2222222

Simplifying
X = 222.2222222