.80x+.05(12-x)=.10(21)

Solution for .80x+.05(12-x)=.10(21) equation:

Simplifying
0.80x + 0.05(12 + -1x) = 0.10(21)
0.80x + (12 * 0.05 + -1x * 0.05) = 0.10(21)
0.80x + (0.6 + -0.05x) = 0.10(21)

Reorder the terms:
0.6 + 0.80x + -0.05x = 0.10(21)

Combine like terms: 0.80x + -0.05x = 0.75x
0.6 + 0.75x = 0.10(21)

Multiply 0.10 * 21
0.6 + 0.75x = 2.1

Solving
0.6 + 0.75x = 2.1

Solving for variable 'x'.

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

Add '-0.6' to each side of the equation.
0.6 + -0.6 + 0.75x = 2.1 + -0.6

Combine like terms: 0.6 + -0.6 = 0.0
0.0 + 0.75x = 2.1 + -0.6
0.75x = 2.1 + -0.6

Combine like terms: 2.1 + -0.6 = 1.5
0.75x = 1.5

Divide each side by '0.75'.
x = 2

Simplifying
x = 2