8.1a-9.9=21.69

Solution for 8.1a-9.9=21.69 equation:

Simplifying
8.1a + -9.9 = 21.69

Reorder the terms:
-9.9 + 8.1a = 21.69

Solving
-9.9 + 8.1a = 21.69

Solving for variable 'a'.

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

Add '9.9' to each side of the equation.
-9.9 + 9.9 + 8.1a = 21.69 + 9.9

Combine like terms: -9.9 + 9.9 = 0.0
0.0 + 8.1a = 21.69 + 9.9
8.1a = 21.69 + 9.9

Combine like terms: 21.69 + 9.9 = 31.59
8.1a = 31.59

Divide each side by '8.1'.
a = 3.9

Simplifying
a = 3.9