.7(X+80)+.1X=72

Solution for .7(X+80)+.1X=72 equation:

Simplifying
0.7(X + 80) + 0.1X = 72

Reorder the terms:
0.7(80 + X) + 0.1X = 72
(80 * 0.7 + X * 0.7) + 0.1X = 72
(56 + 0.7X) + 0.1X = 72

Combine like terms: 0.7X + 0.1X = 0.8X
56 + 0.8X = 72

Solving
56 + 0.8X = 72

Solving for variable 'X'.

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

Add '-56' to each side of the equation.
56 + -56 + 0.8X = 72 + -56

Combine like terms: 56 + -56 = 0
0 + 0.8X = 72 + -56
0.8X = 72 + -56

Combine like terms: 72 + -56 = 16
0.8X = 16

Divide each side by '0.8'.
X = 20

Simplifying
X = 20