0.1a+0.2(12-a)=1.9

Solution for 0.1a+0.2(12-a)=1.9 equation:

Simplifying
0.1a + 0.2(12 + -1a) = 1.9
0.1a + (12 * 0.2 + -1a * 0.2) = 1.9
0.1a + (2.4 + -0.2a) = 1.9

Reorder the terms:
2.4 + 0.1a + -0.2a = 1.9

Combine like terms: 0.1a + -0.2a = -0.1a
2.4 + -0.1a = 1.9

Solving
2.4 + -0.1a = 1.9

Solving for variable 'a'.

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

Add '-2.4' to each side of the equation.
2.4 + -2.4 + -0.1a = 1.9 + -2.4

Combine like terms: 2.4 + -2.4 = 0.0
0.0 + -0.1a = 1.9 + -2.4
-0.1a = 1.9 + -2.4

Combine like terms: 1.9 + -2.4 = -0.5
-0.1a = -0.5

Divide each side by '-0.1'.
a = 5

Simplifying
a = 5