-0.8(a+12)=0.4(a-15)

Solution for -0.8(a+12)=0.4(a-15) equation:

Simplifying
-0.8(a + 12) = 0.4(a + -15)

Reorder the terms:
-0.8(12 + a) = 0.4(a + -15)
(12 * -0.8 + a * -0.8) = 0.4(a + -15)
(-9.6 + -0.8a) = 0.4(a + -15)

Reorder the terms:
-9.6 + -0.8a = 0.4(-15 + a)
-9.6 + -0.8a = (-15 * 0.4 + a * 0.4)
-9.6 + -0.8a = (-6 + 0.4a)

Solving
-9.6 + -0.8a = -6 + 0.4a

Solving for variable 'a'.

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

Add '-0.4a' to each side of the equation.
-9.6 + -0.8a + -0.4a = -6 + 0.4a + -0.4a

Combine like terms: -0.8a + -0.4a = -1.2a
-9.6 + -1.2a = -6 + 0.4a + -0.4a

Combine like terms: 0.4a + -0.4a = 0.0
-9.6 + -1.2a = -6 + 0.0
-9.6 + -1.2a = -6

Add '9.6' to each side of the equation.
-9.6 + 9.6 + -1.2a = -6 + 9.6

Combine like terms: -9.6 + 9.6 = 0.0
0.0 + -1.2a = -6 + 9.6
-1.2a = -6 + 9.6

Combine like terms: -6 + 9.6 = 3.6
-1.2a = 3.6

Divide each side by '-1.2'.
a = -3

Simplifying
a = -3