-.1(a+12)=-2.1(a+1)

Solution for -.1(a+12)=-2.1(a+1) equation:

Simplifying
-0.1(a + 12) = -2.1(a + 1)

Reorder the terms:
-0.1(12 + a) = -2.1(a + 1)
(12 * -0.1 + a * -0.1) = -2.1(a + 1)
(-1.2 + -0.1a) = -2.1(a + 1)

Reorder the terms:
-1.2 + -0.1a = -2.1(1 + a)
-1.2 + -0.1a = (1 * -2.1 + a * -2.1)
-1.2 + -0.1a = (-2.1 + -2.1a)

Solving
-1.2 + -0.1a = -2.1 + -2.1a

Solving for variable 'a'.

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

Add '2.1a' to each side of the equation.
-1.2 + -0.1a + 2.1a = -2.1 + -2.1a + 2.1a

Combine like terms: -0.1a + 2.1a = 2a
-1.2 + 2a = -2.1 + -2.1a + 2.1a

Combine like terms: -2.1a + 2.1a = 0.0
-1.2 + 2a = -2.1 + 0.0
-1.2 + 2a = -2.1

Add '1.2' to each side of the equation.
-1.2 + 1.2 + 2a = -2.1 + 1.2

Combine like terms: -1.2 + 1.2 = 0.0
0.0 + 2a = -2.1 + 1.2
2a = -2.1 + 1.2

Combine like terms: -2.1 + 1.2 = -0.9
2a = -0.9

Divide each side by '2'.
a = -0.45

Simplifying
a = -0.45