(1.3-2.1a)(-4.2)=3.36

Solution for (1.3-2.1a)(-4.2)=3.36 equation:

Simplifying
(1.3 + -2.1a)(-4.2) = 3.36

Reorder the terms for easier multiplication:
-4.2(1.3 + -2.1a) = 3.36
(1.3 * -4.2 + -2.1a * -4.2) = 3.36
(-5.46 + 8.82a) = 3.36

Solving
-5.46 + 8.82a = 3.36

Solving for variable 'a'.

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

Add '5.46' to each side of the equation.
-5.46 + 5.46 + 8.82a = 3.36 + 5.46

Combine like terms: -5.46 + 5.46 = 0.00
0.00 + 8.82a = 3.36 + 5.46
8.82a = 3.36 + 5.46

Combine like terms: 3.36 + 5.46 = 8.82
8.82a = 8.82

Divide each side by '8.82'.
a = 1

Simplifying
a = 1